Knipling-Bushland U.S. Livestock Insects Research Laboratory

The profitability of livestock activities can be diminished significantly by the effects of parasites. Economic losses caused by cattle parasites in Brazil were estimated on an annual basis, considering the total number of animals at risk and the potential detrimental effects of parasitism on cattle productivity. Estimates in U.S. dollars (USD) were based on reported yield losses among untreated animals and reflected some of the effects of parasitic diseases. Relevant parasites that affect cattle productivity in Brazil, and their economic impact in USD billions include: gastrointestinal nematodes - $7.11; cattle tick (Rhipicephalus (Boophilus) microplus) - $3.24; horn fly (Haematobia irritans) - $2.56; cattle grub (Dermatobia hominis) - $0.38; New World screwworm fly (Cochliomyia hominivorax) - $0.34; and stable fly (Stomoxys calcitrans) - $0.34. The combined annual economic loss due to internal and external parasites of cattle in Brazil considered here was estimated to be at least USD 13.96 billion. These findings are discussed in the context of methodologies and research that are required in order to improve the accuracy of these economic impact assessments. This information needs to be taken into consideration when developing sustainable policies for mitigating the impact of parasitism on the profitability of Brazilian cattle producers.

Journal Article Boophilus annulatus and B. microplus: Laboratory Tests of Insecticides Get access R. O. Drummond, R. O. Drummond Entomology Research Division, Agric. Res. Serv., USDA, Kerrville, Texas 78028 Search for other works by this author on: Oxford Academic PubMed Google Scholar S. E. Ernst, S. E. Ernst Entomology Research Division, Agric. Res. Serv., USDA, Kerrville, Texas 78028 Search for other works by this author on: Oxford Academic PubMed Google Scholar J. L. Trevino, J. L. Trevino Entomology Research Division, Agric. Res. Serv., USDA, Kerrville, Texas 78028 Search for other works by this author on: Oxford Academic PubMed Google Scholar W. J. Gladney, W. J. Gladney Entomology Research Division, Agric. Res. Serv., USDA, Kerrville, Texas 78028 Search for other works by this author on: Oxford Academic PubMed Google Scholar O. H. Graham O. H. Graham Entomology Research Division, Agric. Res. Serv., USDA, Kerrville, Texas 78028 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Economic Entomology, Volume 66, Issue 1, 1 February 1973, Pages 130–133, https://doi.org/10.1093/jee/66.1.130 Published: 01 February 1973 Article history Received: 18 April 1972 Published: 01 February 1973

Toward the end of the nineteenth century a complex of problems related to ticks and tick-borne diseases of cattle created a demand for methods to control ticks and reduce losses of cattle. The discovery and use of arsenical solutions in dipping vats for treating cattle to protect them against ticks revolutionized tick and tick-borne disease control programmes. Arsenic dips for cattle were used for about 40 years before the evolution of resistance of ticks to the chemical, and the development and marketing of synthetic organic acaricides after World War II provided superior alternative products. Most of the major groups of organic pesticides are represented on the list of chemicals used to control ticks on cattle. Unfortunately, the successive evolution of resistance of ticks to acaricides in each chemical group with the concomitant reduction in the usefulness of a group of acaricides is a major reason for the diversity of acaricides. Whether a producer chooses a traditional method for treating cattle with an acaricide or uses a new method, he must recognize the benefits, limitations and potential problems with each application method and product. Simulation models and research were the basis of recommendations for tick control strategies advocating approaches that reduced reliance on acaricides. These recommendations for controlling ticks on cattle are in harmony with recommendations for reducing the rate of selection for acaricide resistance. There is a need to transfer knowledge about tick control and resistance mitigation strategies to cattle producers.

BACKGROUND: Ticks are regarded as the most relevant vectors of disease-causing pathogens in domestic and wild animals. The cattle tick, Rhipicephalus (Boophilus) microplus, hinders livestock production in tropical and subtropical parts of the world where it is endemic. Tick microbiomes remain largely unexplored. The objective of this study was to explore the R. microplus microbiome by applying the bacterial 16S tag-encoded FLX-titanium amplicon pyrosequencing (bTEFAP) technique to characterize its bacterial diversity. Pyrosequencing was performed on adult males and females, eggs, and gut and ovary tissues from adult females derived from samples of R. microplus collected during outbreaks in southern Texas. RESULTS: Raw data from bTEFAP were screened and trimmed based upon quality scores and binned into individual sample collections. Bacteria identified to the species level include Staphylococcus aureus, Staphylococcus chromogenes, Streptococcus dysgalactiae, Staphylococcus sciuri, Serratia marcescens, Corynebacterium glutamicum, and Finegoldia magna. One hundred twenty-one bacterial genera were detected in all the life stages and tissues sampled. The total number of genera identified by tick sample comprised: 53 in adult males, 61 in adult females, 11 in gut tissue, 7 in ovarian tissue, and 54 in the eggs. Notable genera detected in the cattle tick include Wolbachia, Coxiella, and Borrelia. The molecular approach applied in this study allowed us to assess the relative abundance of the microbiota associated with R. microplus. CONCLUSIONS: This report represents the first survey of the bacteriome in the cattle tick using non-culture based molecular approaches. Comparisons of our results with previous bacterial surveys provide an indication of geographic variation in the assemblages of bacteria associated with R. microplus. Additional reports on the identification of new bacterial species maintained in nature by R. microplus that may be pathogenic to its vertebrate hosts are expected as our understanding of its microbiota expands. Increased awareness of the role R. microplus can play in the transmission of pathogenic bacteria will enhance our ability to mitigate its economic impact on animal agriculture globally. This recognition should be included as part of analyses to assess the risk for re-invasion of areas like the United States of America where R. microplus was eradicated.

Two species of cattle fever ticks, Boophilus annulatus and B. microplus, were eradicated from the southern United States in a cooperative state-federal program that began in 1907 and was successfully completed in 1960. These vectors were eliminated from an area of approximately 700,000 sq. miles (1,813,000 km2), primarily by dipping cattle and other livestock in an arsenical solution on a schedule shorter than the time required for completion of the parasitic phase of the life cycle of the female ticks, that is, once every 14–18 days. Bovine babesiosis disappeared from the U.S. after the tick vectors were eradicated, and the resultant savings to the livestock industry are estimated to exceed U.S. 1 billion per year. Similar eradication programs in the U.S. Virgin Islands, Soutli America, and Australia have not been successful. During 1960–1972, three species of African ticks were eliminated from the United States before they could become firmly established, but an infestation of Amblyomma variegatum was discovered in Puerto Rico in 1974 and has not yet been eradicated. Psoroptic scabies of sheep was eradicated from a few European countries, Australia and New Zealand before 1900, Canada in 1927, and the United States in 1970. For other acarine parasites the goal for the most part has been control, not eradication. Screwworms were eradicated from Florida and adjoining southeastern states in 1959 by the release of large numbers of sexually sterilized male flies. A similar program that was launched in the Southwest in 1962 is not complete but now that Mexico has joined the effort, eradication from both countries appears nearer realization. Cattle grubs, Hypoderma spp., have so far defied all attempts at eradication, even though very high levels of control, >99%, have been achieved in several countries. Efforts to eradicate other species, e.g., horn flies and stable flies, are confined to research on techniques.

Ecological specialization to restricted diet niches is driven by obligate, and often maternally inherited, symbionts in many arthropod lineages. These heritable symbionts typically form evolutionarily stable associations with arthropods that can last for millions of years. Ticks were recently found to harbour such an obligate symbiont, Coxiella-LE, that synthesizes B vitamins and cofactors not obtained in sufficient quantities from blood diet. In this study, the examination of 81 tick species shows that some Coxiella-LE symbioses are evolutionarily stable with an ancient acquisition followed by codiversification as observed in ticks belonging to the Rhipicephalus genus. However, many other Coxiella-LE symbioses are characterized by low evolutionary stability with frequent host shifts and extinction events. Further examination revealed the presence of nine other genera of maternally inherited bacteria in ticks. Although these nine symbionts were primarily thought to be facultative, their distribution among tick species rather suggests that at least four may have independently replaced Coxiella-LE and likely represent alternative obligate symbionts. Phylogenetic evidence otherwise indicates that cocladogenesis is globally rare in these symbioses as most originate via horizontal transfer of an existing symbiont between unrelated tick species. As a result, the structure of these symbiont communities is not fixed and stable across the tick phylogeny. Most importantly, the symbiont communities commonly reach high levels of diversity with up to six unrelated maternally inherited bacteria coexisting within host species. We further conjecture that interactions among coexisting symbionts are pivotal drivers of community structure both among and within tick species.

Here, economic losses caused by cattle parasites in Mexico were estimated on an annual basis. The main factors taken into consideration for this assessment included the total number of animals at risk, potential detrimental effects of parasitism on milk production or weight gain, and records of condemnation on livestock byproducts. Estimates in US dollars (US$) were based on reported yield losses in untreated animals. These estimates reflect the major effects on cattle productivity of six parasites, or parasite group. The potential economic impact (US$ millions) was: gastrointestinal nematodes US$ 445.10; coccidia (Eimeria spp.) US$ 23.78; liver fluke (Fasciola hepatica) US$ 130.91; cattle tick (Rhipicephalus microplus) US$ 573.61; horn fly (Haematobia irritans) US$ 231.67; and stable fly (Stomoxys calcitrans) US$ 6.79. Overall, the yearly economic loss due to the six major parasites of cattle in Mexico was estimated to be US$ 1.41 billion. Considering that the national cattle herd registered in 2013 included 32.40 million head, the estimated yearly loss per head was US$ 43.57. The limitations of some of the baseline studies used to develop these estimates, particularly when extrapolated from local situations to a national scale, are acknowledged. However, the general picture obtained from the present effort demonstrates the magnitude and importance of cattle parasitism in Mexico and the challenges to maximize profitability by the livestock industry without adapting sustainable and integrated parasite control strategies.

Chapter 5 Microbial Indicators of Soil Quality R. F. Turco, R. F. Turco Laboratory for Soil Microbiology Purdue University, West Lafayette, IndianaSearch for more papers by this authorA. C. Kennedy, A. C. Kennedy USDA-ARS, Pullman, WashingtonSearch for more papers by this authorM. D. Jawson, M. D. Jawson Kerr Laboratory USEPA, Ada, OklahomaSearch for more papers by this author R. F. Turco, R. F. Turco Laboratory for Soil Microbiology Purdue University, West Lafayette, IndianaSearch for more papers by this authorA. C. Kennedy, A. C. Kennedy USDA-ARS, Pullman, WashingtonSearch for more papers by this authorM. D. Jawson, M. D. Jawson Kerr Laboratory USEPA, Ada, OklahomaSearch for more papers by this author Book Editor(s):J.W. Doran, J.W. DoranSearch for more papers by this authorD.C. Coleman, D.C. ColemanSearch for more papers by this authorD.F. Bezdicek, D.F. BezdicekSearch for more papers by this authorB.A. Stewart, B.A. StewartSearch for more papers by this author First published: 01 May 1994 https://doi.org/10.2136/sssaspecpub35.c5Citations: 20Book Series:SSSA Special Publications AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onEmailFacebookTwitterLinkedInRedditWechat Summary The quality of soil can impact land use, sustainability, and productivity. Human and animal health is closely linked to soil productivity and environmental quality. Soil microbial processes are an integral part of soil quality, and a better understanding of these processes and microbial community structure is needed. Assessment of microbial diversity may indicate profound differences in soils with respect to microbial populations and functions. The most obvious attempt at developing microbial indicators for use in environmental assessment is coliform bacteria. To provide a better understanding of the role of soil microbiology in soil quality, it is necessary to discuss the methods that best address and estimate microbial form and function in soil. Microbial diversity indices can function as bio-indicators by showing the community stability and describing the ecological dynamics of a community and impacts of stress on that community. References Alef,K.,T.Beck,L.Zelles, andD.Kleiner.1988.A comparison of methods to estimate microbial biomass and N-mineralization in agricultural and grassland soils.Soil Biol. Biochem. 20: 561–565. 10.1016/0038-0717(88)90073-9 CASWeb of Science®Google Scholar Anderson,J.P.E., andK.H.Domsch.1978.A physiological method for the quantitative measurement of microbial biomass in soils.Soil Biol. Biochem. 10: 215–221. 10.1016/0038-0717(78)90099-8 CASWeb of Science®Google Scholar Anderson,T.H., andK.H.Domsch.1985.Maintenance requirements of actively metabolizing microbial populations under in situ conditions.Soil. Biol. Biochem. 17: 197–203. 10.1016/0038-0717(85)90115-4 CASWeb of Science®Google Scholar Anderson,T.H., andK.H.Domsch.1990.Application of eco-physiological quotients (qCO2 andqD) on microbial biomasses from soils of different cropping histories.Soil Biol. Biochem. 22: 251–255. 10.1016/0038-0717(90)90094-G Web of Science®Google Scholar Atlas,R.M.1984a. Use of microbial diversity measurements to assess enviornmental stress. p. 540–545.In C.A. Reddy, and M.J. Klug (ed.) Current perspectives in microbial ecology.Am. Soc. for Microbiol,Washington, DC. Google Scholar Balkwill,D.L.,F.R.Leach,J.T.Wilson,J.F.McNabb, andD.C.White.1988.Equivalence of microbial biomass measures based on membrane lipid and cell wall components, adenosine, triphosphate and direct counts in subsurface aquifer sediments.Microb. Ecol. 16: 73–84. 10.1007/BF02097406 CASPubMedWeb of Science®Google Scholar Bej,A.K.,J.L.Dicesare,L.Haff, andR.M.Atlas.1991.Detection ofEscherichia coli andShigella spp. in water by using the polymerase chain reaction and gene probes foruid.Appl. Environ. Microbiol. 57: 1013–1017. CASPubMedWeb of Science®Google Scholar Bej,A.K.,S.C.McCarty, andR.M.Atlas.1990.Detection of coliform bacteria andEscherichia coli by multiplex polymerase chain reaction: comparison with defined substrate and plating methods for water quality monitoring.Appl. Environ. Microbiol. 56: 2429–2432. Google Scholar Bobbie,R.J., andD.C.White.1980.Characterization of benthic microbial community structure by high-resolution gas chromatography of fatty acid methyl esters.Appl. Environ. Microbiol. 39: 1212–1222. CASPubMedWeb of Science®Google Scholar Bolton,H.,L.F.Elliott,R.I.Papendick, andD.F.Bezdicek.1985.Soil microbial biomass and selected soil enzyme activities: Effects of fertilization and cropping practices.Soil Biol. Biochem. 17: 297–302. 10.1016/0038-0717(85)90064-1 CASWeb of Science®Google Scholar Brock,T.D., andM.T.Madigan.1991. Major microbial disease. p. 556–557. In Biology of microorganisms. 6th edPrentice Hall, Englewood Cliffs,NJ. Google Scholar Brockman,F.J., andD.F.Bezdicek.1989.Diversity of serogroups ofRhizobium leguminosarum biovarviceae in the Palouse region of Eastern Washington as indicated by plasmid profiles, intrinsic antibiotic resistance and topography.Appl. Environ. Microbiol. 55: 109–115. CASPubMedWeb of Science®Google Scholar Bruce,K.D.,W.D.Hiorns,J.L.Hobman,A.M.Osborn,P.Strike, andD.A.Ritchie.1992.Amplification of DNA from native populations of soil bacteria using polymerase chain reaction.Appl. Environ. Microbiol. 58: 3413–3416. CASPubMedWeb of Science®Google Scholar Burns,R.G.1978. Soil enzymes.Academic Press,New York. 10.1007/BF01922997 Web of Science®Google Scholar Byrd,J.J.,H.-S.Xu, andR.R.Colwell.1991.Viable but nonculturable bacteria in drinking water.Appl. Environ. Microbiol. 57: 875–878. 10.1128/AEM.57.3.875-878.1991 CASPubMedWeb of Science®Google Scholar Calabrese,V.G.M.,W.E.Holben, andA.J.Sexstone.1991. Assessment of diversity of 2,4-D-catabolic plasmids in bacteria isolated from different soils. p. 260. In Agronomy abstracts.ASA, Madison,WI. Google Scholar Clark,F.E.1965. The concept of competition in microbial ecology. p. 339–344.In K.F. Baker, and W.C. Snyder (ed.) Ecology of soil-borne plant pathogens.Univ. of California Press,Berkeley, CA. Google Scholar Collins,M.D., andD.Jones.1981.Distribution of isoprenoid quinone structural types in bacteria and their taxonomic implication.Microbiol. Rev. 45: 316–354. 10.1128/MMBR.45.2.316-354.1981 CASPubMedWeb of Science®Google Scholar Cundell,A.M.1977.The role of microorganisms in the revegetation of strip-mined land in the western United States.J. Range Manage. 30: 229–305. 10.2307/3897311 Google Scholar DeBoer,S.H., andM.Sasser.1986.Differentiation ofErwinia carotovora spp.carotovora andE. carotovora spp.atrosptica on the basis of fatty acid composition.Can. J. Microbiol. 32: 796–800. 10.1139/m86-146 CASWeb of Science®Google Scholar Dick,W.A.1984.Influence of long-term tillage and crop rotation combinations on soil enzyme activities.Soil Sci. Soc. Am. J. 48: 569–584. 10.2136/sssaj1984.03615995004800030020x CASWeb of Science®Google Scholar Doran,J.W.1980.Soil microbial and biochemical changes associated with reduced tillage.Soil Sci. Soc. Am. J. 44: 765–771. 10.2136/sssaj1980.03615995004400040022x CASWeb of Science®Google Scholar Doran,J.W.,D.G.Fraser,M.N.Culik, andW.C.Liebhart.1987.Influence of alternative and conventional agriculture management on soil microbial processes and nitrogen availability.Am. J. Altern. Agric. 2: 99–106. Google Scholar Drucker,D.B.1976.Gas-liquid chromatographic chemotaxonomy.Methods Microbiol. 9: 51–125. 10.1016/S0580-9517(09)70040-6 CASGoogle Scholar EMAP Monitor.1992. Design of comprehensive monitoring program. USEPA Rep. 600/M-91.051. USEPA,Washington, DC. Google Scholar Fahy,P.C., andA.C.Hayward.1983. Media and methods for isolation and diagnostic tests.In P.G. Fahy A.C. Hayward (ed.) p. 337–378. Plant and bacterial diseases: A diagnostic guide.Academic Press,New York. Google Scholar Federle,T.W.1988.Mineralization of monosubstituted aromatic compounds in unsaturated and saturated subsurface soils.Can. J. Microbiol. 34: 1037–1042. 10.1139/m88-182 CASWeb of Science®Google Scholar Findlay,R.H.,G.King, andL.Watling.1989.Efficacy of phospholipid analysis in determining microbial biomass in sediments.Appl. Environ. Microbiol. 55: 2888–2893. 10.1128/AEM.55.11.2888-2893.1989 CASPubMedWeb of Science®Google Scholar Findlay,R.H.,M.B.Trexler,J.B.Guckert, andD.C.White.1990.Laboratory study of disturbance in marine sediments: Response of microbial community.Marine Ecol. Prog. Ser. 62: 121–133. 10.3354/meps062121 Web of Science®Google Scholar .1983. S.B. Flexner The Random House dictionary of English language. 2nd edRandom House,New York. Google Scholar Frankland,J.C.,D.K.Lindley, andM.J.Swift.1978.A comparison of two methods for the estimation of mycelial biomass in leaf litter.Soil Biol. Biochem. 10: 323–333. 10.1016/0038-0717(78)90030-5 Web of Science®Google Scholar Fredrickson,J.K.,D.L.Balkwill,J.M.Zachara,S.M.W.Li,F.J.Brockman, andM.A.Simmons.1991.Physiological diversity and distributions of heterotrophic bacteria in deep cretaceous sediments of the Atlantic coastal plain.Appl. Environ. Microbiol. 57: 402–411. 10.1128/AEM.57.2.402-411.1991 CASPubMedWeb of Science®Google Scholar Frederickson,J.K.,D.F.Bezdicek,F.E.Brockman, andS.W.Li.1988.Enumeration ofTn5 mutant bacteria in soil by most-probable-number DNA hybridization procedure and antibiotic resistance.Appl. Environ. Microbiol. 54: 446–453. PubMedWeb of Science®Google Scholar Fresquez,R.R.,E.F.Aldon, andW.C.Lindemann.1986.Microbial diversity of fungal genera in reclaimed coal mine spoils and soils.Reclam. Reveg. Res. 4(3): 245–258. Google Scholar Garland,J.L., andA.L.Mills.1991.Classification and characterization of heterotrophic microbial communities on the basis of patterns of community-level-sole-carbon-source utilization.Appl. Environ. Microbiol. 57: 2351–2359. 10.1128/AEM.57.8.2351-2359.1991 CASPubMedWeb of Science®Google Scholar Goldfine,H.1972. Comparative aspects of bacterial lipids. p. 1–51.In A.H. Rose, and D.W. Tempest (ed.) Advances in microbial physiology.Academic Press,New York. Google Scholar Goor,M. J.,L.Mergaert,C.Verdonck,R.Ryckaert,J.Vantomme,K.Swings,J.Kersters, andLeyDe.1984.The use of API systems in the identification of phytopathogenic bacteria.Med. Fac. Landbouwwetl. Rijksuniv. Gent. 49: 499–507. Google Scholar Graham,J.H.,J.S.Hartung,R.E.Stall, andA.R.Chase.1990.Pathological restriction-fragment length polymorphism, and fatty acid profile relationships betweenXanthomonas campestris from citrus and noncitrus hosts.Phytopathol. 80: 829–836. 10.1094/Phyto-80-829 CASWeb of Science®Google Scholar Guckert,J.B., andD.C.White.1986. Phospholipid, ester-linked fatty acid analysis in microbial ecology. p. 455–459.in F. Megusar, and M. Gantar (ed.) Perspectives in microbial ecology. Proc. of the 4th Int. Symp. of Microbial Ecology, Ljubljana, Yugoslavia. 24-29 Aug. 1986. Google Scholar Hawksworth,D.L., andL.A.Mound.1991. Biodiversity database: The crucial significance of collections. p. 17–31.In D.L. Hawksworth (ed.) The biodiversity of microorganism and invertebrates: Its role in sustainable agriculture.CAB International,Wallingford Oxon, UK. Google Scholar Holben,W.E.,J.K.Jansson,B.K.Chelm, andJ.M.Tiedje.1988.DNA probe method for the detection of specific microorganisms in the soil bacterial community.Appl. Environ. Microbiol. 54: 703–711. 10.1128/AEM.54.3.703-711.1988 CASPubMedWeb of Science®Google Scholar Holloway,J.D.1985.Moths as indicator organisms for categorizing rain forest and monitoring changes and regeneration processes. p. 235–242.In A.C. Chadwick and S.L. Sutton (ed.)Tropical rain-forest. Leeds Philosophical and Literary Society, Leeds. Google Scholar Holloway,J.D., andN.E.Stork.1991. The dimension of biodiversity: The use of invertebrates as indicators of human impact. p. 37–63.In D.L. Hawksworth (ed.) The biodiversity of microorganism and invertebrates: Its role in sustainable agriculture.CAB International,Wallingford, Oxon, UK. Google Scholar Holm,E., andV.Jensen.1980.Microfungi of a Danish beech forest.Holarctic Ecol. 3(1): 19–25. Google Scholar Hugh,R., andE.Leifson.1953.The taxonomic significance of fermentative versus oxidative metabolism of carbohydrates by various Gram bacteria.J. Bacteriol. 66: 24–26. 10.1128/JB.66.1.24-26.1953 CASPubMedWeb of Science®Google Scholar Insam,H., andK.H.Domsch.1988.Relationship between soil organic carbon and microbial biomass on chronosequences of reclamation sites.Microbiol. Ecol. 15: 177–188. 10.1007/BF02011711 Web of Science®Google Scholar Insam,H., andK.Hasselwandter.1989.Metabolic quotient of the soil microfloral in relation to plant succession.Oecologia. 79: 174–178. 10.1007/BF00388474 CASPubMedWeb of Science®Google Scholar Jenkinson,D.S.1988. Determination of microbial carbon and nitrogen in soil. p. 368–386.In J.B. Wilson (ed.)Advances in nitrogen cycling. CAB International,Wallingford, England. Google Scholar Jenkinson,D.S., andJ.M.Ladd.1981. Microbial biomass in soil: Movement and turnover p. 415–471.In E.A. Paul and J.M. Ladd (ed.) Soil biochemistry.Marcel Dekker,New York. Google Scholar Jensen,V.1968. The plate count technique. p. 158–170.In T.R.G. Gray, and D. Parkinson (ed.) The ecology of soil bacteria.University Press, Liverpool,England. Web of Science®Google Scholar Johnson,K.G.,M.C.Silva,C.R.MacKenzie,H.Schneider, andJ.D.Fontana.1989.Microbial degradation of hemicellulosic materials.Appl. Biochem. Biotech. 20: 245–258. 10.1007/BF02936486 Web of Science®Google Scholar Josephson,K.L.,S.D.Pillai,J.Way,C.P.Gerba, andI.L.Pepper.1991.Fecal coliforms in soil detected by polymerase chain reaction and DNA-DNA hybridizaiton.Siol Sci. Soc. Am. J. 55: 1326–1332. 10.2136/sssaj1991.03615995005500050022x CASWeb of Science®Google Scholar Kamicker,B.J., andW.J.Brill.1986.Identification ofBradyrhizobium japonicum nodule isolates from Wisconsin soybean farms.Appl. Environ. Microbiol. 51: 487–492. PubMedWeb of Science®Google Scholar Knapp.C.M.,D.R.Marmorek,J.P.Baker,K.W.Thornton, andJ.M.Klopatek.1991. Indicator development strategy for the environmental monitoring and assessment program.USEPA Rep. 600/3-91/023. USEPA,Corvallis, OR. Google Scholar Konopka,A., andR.F.Turco.1991.Biodegradation of organic compounds in vadose zone and aquifer sediments.Appl. Environ. Microbiol. 57: 2260–2268. 10.1128/AEM.57.8.2260-2268.1991 CASPubMedWeb of Science®Google Scholar Krieg,N.R., andJ.G.Holt.1984. Bergey's manual of systematic bacteriology.Williams & Wilkens,Baltimore, MD. 1 Google Scholar Kuhn,I.,G.Allestam,T.A.Stenstrom, andR.Mollby.1991.Biochemical fingerprinting of water coliform bacteria, a new method for measuring phenotypic diversity and for comparing different bacterial populations.Appl. Environ. Microbiol. 57: 3171–3177. PubMedWeb of Science®Google Scholar Ladd,J.N.1985. Soil enzymes. p. 175–221.In D. Vaughan, and R.E. Malcolm (ed.) Soil organic matter and biological activity.Nijhoff and Junk Publ., The Hague,Netherlands. 10.1007/978-94-009-5105-1_6 Google Scholar Lambert,B.,P.Meire,H.Joos,P.Lens, andJ.Swings.1990.Fast-growing, aerobic, heterotrophic bacteria from the rhizosphere of young sugar beet plants.Appl. Environ. Microbiol. 56: 3381–3381. Google Scholar Lambshed,P.J.D.,H.M.Platt, andK.M.Shaw.1983.The detection of differences among assemblages of marine benthic species based on an assessment of dominance and diversity.J. Nat. Hist. 17: 859–874. Google Scholar Lechevalier,M.P.1977.Lipids in bacterial taxonomy—a taxonomist's view.Crit. Rev. Microbiol. 5: 109–210. 10.3109/10408417709102311 CASPubMedWeb of Science®Google Scholar Lee,K.E.1985. Earthworms: Their ecology and relationships with soils and land use.Academic Press,New York. Google Scholar Lee,K.E.1991. The diversity of soil organisms. p. 72–89.In D.L. Hawksworth (ed.) The biodiversity of microorganisms and invertebrates; Its role in sustainable agriculture.CASAFA Rep. Ser. 4. Redwood Press Ltd.,England. Google Scholar Lenhard,G.1956.Die dehydrogenase—activitat des Bodens als mass für mikroorganis-mentätigkeit im Boden.Z. Pflanzenernaehr. Bodenkd. 73: 1–11. 10.1002/jpln.19560730102 CASGoogle Scholar Lennon,E., andB.T.DeCicco.1991.Plasmids ofPseudomonas cepacia strains of diverse origins.Appl. Environ. Microbiol. 57: 2345–2350. 10.1128/AEM.57.8.2345-2350.1991 CASPubMedWeb of Science®Google Scholar Lipman,J.G.,H.McLean, andH.C.Lint.1916.Sulphur oxidation in soils and its effect on the availability of mineral phosphates.Soil Sci. 1: 533–539. 10.1097/00010694-191606000-00002 CASGoogle Scholar Martin,P.A.W., andR.S.Travers.1989.Worldwide abundance and distribution ofBacillus thuringienisis isolates.Appl. Eviron. Microbiol. 55: 2437–2442. PubMedWeb of Science®Google Scholar Martynuik,S., andG.H.Wagner.1978.Quantitative and qualitative examination of soil microflora associated with different management systems.Soil Sci. 125: 340. Google Scholar May,R.M.1988.How many species are there on earth.Sci. 241: 1441–1449. 10.1126/science.241.4872.1441 CASADSPubMedWeb of Science®Google Scholar McKinley,V.L.,T.W.Federle, andJ.R.Vestal.1982.Effects of hydrocarbons on the plant litter microbiota of an Arctic lake.Appl. Environ. Microbiol. 43: 129–135. CASPubMedWeb of Science®Google Scholar Mergaert,J. L.,K.Verdonck,J.Kersters,J.M.Swings,J.Boeufgras, andLayDe.1984.Numerical taxonomy ofErwinia species using API systems.J. Gen. Microbiol. 130: 1893–1910. Web of Science®Google Scholar Miller,L.T.1982.A single derivitization method for bacterial fatty acid methyl esters including hydroxy acids.J. Clin. Microbiol. 16: 584–586. 10.1128/JCM.16.3.584-586.1982 CASPubMedWeb of Science®Google Scholar Miller,L.T., andT.Berger.1985. Bacteria identification by gas chromatography of whole cell fatty acids. p. 228–241. MIDI Tech. Note 101. MIDI Newark, DE. Google Scholar Miller,W.N., andL.E.CasidaJr..1970.Evidence for muramic acid in soil.Can. J. Microbiol. 16: 299–304. Google Scholar Moorman,T.B.1989.A review of pesticides effects on microorganisms and microbial processes related to soil fertility.J. Prod. Agric. 2: 14–23. 10.2134/jpa1989.0014 Google Scholar Moss,C.,M.A.Lambert, andW.H.Merwin.1974.Comparison of rapid methods for analysis of bacterial fatty acids.Appl. Microbiol. 28: 80–85. CASPubMedWeb of Science®Google Scholar Moss,C.W.1981.Gas-liquid chromatography as an analytical tool in microbiology.J. Chrom. 203: 337–347. 10.1016/S0021-9673(00)80305-2 CASPubMedWeb of Science®Google Scholar Mukherjee,D., andA.C.Gaur.1980.A study of the influence of straw incorporation on soil organic matter maintenance, nutrient release and asymbiotic nitrogen fixation.Zentralbl. Bakteriol. Parasitenkd. Infekttionshr. Hyg. II. 135(8): 663–668. Google Scholar Newell,S.Y.,T.L.Arsuffi, andR.D.Fallon.1988.Fundamental procedures for determining ergosterol content of decaying plant material by liquid chromatography.Appl. Environ. Microbiol. 54: 1876–1879. CASPubMedWeb of Science®Google Scholar Odum,E.P.1969.The strategy of ecosystem development.Science (Washington, DC). 164: 262–270. 10.1126/science.164.3877.262 CASADSPubMedWeb of Science®Google Scholar Office of Technology Assessment.1987. Technologies to maintain biological diversity.OTA,Washington, DC. Google Scholar Picard,C.,C.Ponsonnet,E.Paget,X.Nesme, andP.Simonet.1992.Detection and enumeration of bacteria in soil by direct DNA extraction and polymerase chain reaction.Appl. Environ. Microbiol. 58: 2717–2722. 10.1128/AEM.58.9.2717-2722.1992 CASPubMedWeb of Science®Google Scholar Pillai,S.D.,K.L.Josephson,R.L.Gerba,C.P.Bailey, andI.L.Pepper.1991.Rapid method for processing soil samples for polymerase chain reaction amplification of specific gene sequences.Appl. Environ. Microbiol. 57: 2283–2286. 10.1128/aem.57.8.2283-2286.1991 CASPubMedWeb of Science®Google Scholar Powlson,D.S.,P.C.Brookes, andB.T.Christensen.1987.Measurement of soil microbial biomass provides an early indication of changes in total soil organic matter due to straw incorporation.Soil Biol. Biochem. 19: 159–164. 10.1016/0038-0717(87)90076-9 CASWeb of Science®Google Scholar Ramsay,A.J.,R.E.Stannard, andG.J.Churchman.1986.Effect of conversion from ryegrass pasture to wheat cropping on aggregation and bacterial populations in a silt loam soil in New Zealand.Aust. J. Soil Res. 24: 253–264. 10.1071/SR9860253 Web of Science®Google Scholar Rao,C.R., andB.Venkateswarlu.1981.Distribution of microorganisms in stabilized and unstabilized sand dunes of the Indian desert.J. Arid Environ. 4: 203–207. Google Scholar et alRao,P.S.C.,K.S.V.Edvardsson,L.T.Ou,R.E.Jessup,P.Nkedi-Kizza, andA.G.Hornsby.1986. Spatial variability of pesticide sorption and degradation parameters. p. 100–115.In W.Y. Garner (ed.) Evaluation of pesticide in groundwater.Am. Chem. Soc,Washington, DC. Google Scholar Ringelberg,D.B.,J.D.Davis,G.A.Smith,S.M.Pfiffner,P.D.Nichols,J.S.Nickels,J.M.Hensen,J.T.Wilson,M.Yates,D.H.Kampbell,H.W.Reed,T.T.Stockdale, andD.C.White.1989.Validation of signature polarlipid fattya cid biomarkers for alkane-utilizing bacteria in soils and subsurface sediments of aquifer materials.FEMS Microb. Eco. 62: 39–50. 10.1111/j.1574-6968.1989.tb03656.x CASWeb of Science®Google Scholar Robertson,G.P.,M.A.Huston,F.C.Evans, andJ.M.Tiedje.1988.Spatial variability in a successional plant community patterns of nitrogen availability.Ecol. 69: 1517–1524. 10.2307/1941649 Web of Science®Google Scholar Roszak,D.B., andR.R.Colwell.1987.Survival strategies of bacteria in the natural environment.Microbiol. Rev. 51: 365–379. 10.1128/mr.51.3.365-379.1987 CASPubMedWeb of Science®Google Scholar Segal,W., andR.L.Mancinelli.1987.Extent of regeneration of the microbial community in reclaimed spent oil shale land.J. Environ. Qual. 16: 44–47. 10.2134/jeq1987.00472425001600010009x Web of Science®Google Scholar Shaw,N.1974.Lipid composition as a guide to the classification of bacteria.Adv. Appl. Microbiol. 17: 63. 10.1016/S0065-2164(08)70555-0 CASPubMedGoogle Scholar Smith,J.L., andE.A.Paul.1989. The significance of soil microbial biomass estimations in soil. Soil biochemistry. Vol. 6.Marcel Dekker,New York. Google Scholar Sommerville,C.C.,I.T.Knight,W.L.Straube, andR.R.Cowell.1989.Simple, rapid method for direct isolation of nucleic acids form aquitic environments.Appl. Environ. Microbiol. 55: 548–554. PubMedWeb of Science®Google Scholar Sorheim,R.,V.L.Torsvik, andJ.Goksoyr.1989.Phenotypical divergence between populations of soil bacteria isolated on different media.Microb. Ecol. 17: 181–192. 10.1007/BF02011852 CASPubMedWeb of Science®Google Scholar Sparling,G.P.1981.Heat output of the soil biomass.Soil Biol. Biochem. 13: 373–376. 10.1016/0038-0717(81)90079-1 CASWeb of Science®Google Scholar Stanier,R.Y.,E.A.Adeleberg, andJ.Ingraham.1976. The microbial world.Prentice-Hall, Englewood Cliffs,NJ. Google Scholar Torsvik,V.,J.Goksoy, andF.L.Daae.1990a.High diversity in DNA of soil bacteria.Appl. Environ. Microbiol. 56: 782–787. 10.1128/AEM.56.3.782-787.1990 CASPubMedWeb of Science®Google Scholar Torsvik,V.,K.Salte,R.Sorheim, andJ.Goksoyr.1990b.Comparison of phenotypic diversity and DNA heterogeneity in a population of soil bacteria.Appl. Environ. Microbiol. 56: 776–781. 10.1128/AEM.56.3.776-781.1990 CASPubMedWeb of Science®Google Scholar Troussellier,M., andP.Legendre.1981.A functional evenness index for microbial ecology.Microb. Ecol. 7: 283–296. 10.1007/BF02341423 CASPubMedWeb of Science®Google Scholar Tsai,Y., andB.H.Olson.Rapid method for direct extraction of DNA from soil and sediments.Appl. Enviorn. Microbiol. 57: 1070–1074. Google Scholar Turco,R.F., andD.F.Bezdicek.1987.Diversity within two serogroups ofRhizobium leguminosarum native to soils in the Palouse of Eastern Washington.Ann. Appl. Biol. 111: 103–114. 10.1111/j.1744-7348.1987.tb01437.x Web of Science®Google Scholar Veldkamp,H.,H.Van Gemerden,W.Harder, andH.J.Laanbroek.1984. Competition among bacteria: An overview. p. 279–290.In M.J. Klug, and CA. Reddy (ed.) Current perspectives in microbial ecology.Am. Soc. for Microbiol,Washington, DC. Google Scholar Visser,S., andD.Parkinson.1992.Soil biological criteria as indicators of soil quality: Soil microorganisms.Am. J. Altern. Agric. 7: 33–37. Google Scholar between and plant in Manage. Google Scholar of the microbial biomass by lipid CASADSPubMedWeb of Science®Google Scholar characterization and of the Bacteriol. CASPubMedWeb of Science®Google Scholar by are as Res. CASPubMedWeb of Science®Google Scholar The of biological p. Wilson (ed.) DC. Google Scholar fatty acids in and as indicators of microbial biomass and community structure in agricultural soils.Soil Biol. Biochem. 24: CASWeb of Science®Google Scholar Soil Quality for a

Two patterns of pyrethroid resistance were characterized from Boophilus microplus (Canestrini) collected in Mexico. One was characteristic of a kdr mutation and the other involved esterase and cytochrome P450 enzyme systems. Very high resistance to permethrin, cypermethrin, and flumethrin, not synergized by TPP and PBO and high resistance to DDT, characterized the kdr-like pattern found in the Corrales and San Felipe strains. Esterase and cytochrome P450-dependent resistance was found in the Coatzacoalcos strain. It was characterized by resistance to permethrin, cypermethrin, and flumethrin, synergized by TPP and PBO, but no resistance to DDT. The Coatzacoalcos strain also showed 3.6-fold resistance to the organophosphate coumaphos. This factor appeared to be independent of pyrethroid resistance. Pyrethroid resistance patterns found in Mexico were similar to those found earlier in Australia. The significance of pyrethroid and coumaphos resistance to the U.S. cattle fever tick quarantine is discussed.

Abstract Varroa mites (Varroa destructor Anderson and Trueman, 2000) are becoming resistant to acaricide treatments via metabolic and/or target site desensitivity. Results of a survey of mites from the Carl Hayden AZ lab and from cooperators in five locations (Arizona, California, Florida, Maine, North Dakota) showed that some mites were susceptible to all three acaricides (Amitraz, Coumaphos, Fluvalinate) in the spring of 2003, but by fall most mites were resistant. Mites were resistant to all chemicals, even from beekeepers that do not treat colonies with acaricides. We used esterase native activity gels to test for the presence of specific esterases which might be involved in pesticide resistance in varroa. All mites tested had positive bands for esterase, even those exhibiting susceptibility to some acaricides. Based on the differences between the esterase activity gel profile of the susceptible and cross-resistant V. destructor, it is possible that an esterase-mediated resistance mechanism is operative in the population of the mites we analyzed. However, a combination of other resistance mechanisms may be present which make the esterase activity gel method unreliable for use in identifying varroa mites with multiple resistance.

The levels of resistance to two organophosphate acaricides, coumaphos and diazinon, in several Mexican strains of Boophilus microplus (Canestrini) were evaluated using the FAO larval packet test. Regression analysis of LC50 data revealed a significant cross-resistance pattern between those two acaricides. Metabolic mechanisms of resistance were investigated with synergist bioassays. Piperonyl butoxide (PBO) reduced coumaphos toxicity in susceptible strains, but synergized coumaphos toxicity in resistant strains. There was a significant correlation between PBO synergism ratios and the coumaphos resistance ratios. The results suggest that an enhanced cytochrome P450 monooxygenase (cytP450)-mediated detoxification mechanism may exist in the resistant strains, in addition to the cytP450-mediated metabolic pathway that activates coumaphos. PBO failed to synergize diazinon toxicity in resistant strains, suggesting the cytP450 involved in detoxification were specific. Triphenylphosphate (TPP) synergized toxicity of both acaricides in both susceptible and resistant strains, and there was no correlation between TPP synergism ratios and the LC50 estimates for either acaricide. Esterases may not play a major role in resistance to coumaphos and diazinon in those strains. Bioassays with diethyl maleate (DEM) revealed a significant correlation between DEM synergism ratios and LC50 estimates for diazinon, suggesting a possible role for glutathione S-transferases in diazinon detoxification. Resistance to coumaphos in the Mexican strains of B. microplus was likely to be conferred by both a cytP450-mediated detoxification mechanism described here and the mechanism of insensitive acetylcholinesterases reported elsewhere. The results of this study also underscore the potential risk of coumaphos resistance in B. microplus from Mexico to the U.S. cattle fever tick eradication program.

Amitraz, a formamidine acaricide, plays an important role in the control of the southern cattle tick, Boophilus microplus (Canestrini), and other tick species that infest cattle, dogs, and wild animals. Although resistance to amitraz in B. microplus was previously reported in several countries, the actual measurement of the level of amitraz resistance in ticks has been difficult to determine due to the lack of a proper bioassay technique. We conducted a survey, by using a newly reported technique that was a modification of the standard Food and Agriculture Organization larval packet test, to measure the levels of resistance to amitraz in 15 strains of B. microplus from four major cattle-producing states in Mexico. Low-order resistance (1.68- to 4.58-fold) was detected in 11 of those strains. Our laboratory selection using amitraz on larvae of the Santa Luiza strain, which originated from Brazil, achieved a resistance ratio of 153.93 at F6, indicating the potential for high resistance to this acaricide in B. microplus. Both triphenylphosphate and piperonyl butoxide significantly synergized amitraz toxicity in both resistant and susceptible tick strains. Diethyl maleate synergized amitraz toxicity in one resistant strain but had no effect on the susceptible strain and had minor antagonistic effects on two other resistant strains. Target site insensitivity, instead of metabolic detoxification mechanisms, might be responsible for amitraz resistance observed in the Santa Luiza strain and possibly in other amitraz resistant B. microplus ticks from Mexico. The Santa Luiza strain also demonstrated high resistance to pyrethroids and moderate resistance to organophosphates. Multiple resistance shown in this strain and other B. microplus strains from Mexico poses a significant challenge to the management of B. microplus resistance to acaricides in Mexico.

The ticks Rhipicephalus (Boophilus) annulatus and R. (B.) microplus, commonly known as cattle and southern cattle tick, respectively, impede the development and sustainability of livestock industries throughout tropical and other world regions. They affect animal productivity and wellbeing directly through their obligate blood-feeding habit and indirectly by serving as vectors of the infectious agents causing bovine babesiosis and anaplasmosis. The monumental scientific discovery of certain arthropod species as vectors of infectious agents is associated with the history of research on bovine babesiosis and R. annulatus. Together, R. microplus and R. annulatus are referred to as cattle fever ticks (CFT). Bovine babesiosis became a regulated foreign animal disease in the United States of America (U.S.) through efforts of the Cattle Fever Tick Eradication Program (CFTEP) established in 1906. The U.S. was declared free of CFT in 1943, with the exception of a permanent quarantine zone in south Texas along the border with Mexico. This achievement contributed greatly to the development and productivity of animal agriculture in the U.S. The permanent quarantine zone buffers CFT incursions from Mexico where both ticks and babesiosis are endemic. Until recently, the elimination of CFT outbreaks relied solely on the use of coumaphos, an organophosphate acaricide, in dipping vats or as a spray to treat livestock, or the vacation of pastures. However, ecological, societal, and economical changes are shifting the paradigm of systematically treating livestock to eradicate CFT. Keeping the U.S. CFT-free is a critical animal health issue affecting the economic stability of livestock and wildlife enterprises. Here, we describe vulnerabilities associated with global change forces challenging the CFTEP. The concept of integrated CFT eradication is discussed in reference to global change.

Rhipicephalus sanguineus (Latreille) were collected from the Corozal Army Veterinary Quarantine Center in Panama and characterized for resistance to five classes of acaricides. These ticks were highly resistant to permethrin, DDT, and coumaphos; moderately resistant to amitraz; and not resistant to fipronil when compared with susceptible strains. Resistance to both permethrin and DDT may result from a mutation of the sodium channel. However, synergist studies indicate that enzyme activity is involved. The LC50 estimate for permethrin was lowered further in the Panamanian strain then in susceptible strains with the addition of triphenylphosphate (TPP), but not with the addition ofpiperonyl butoxide (PBO). This suggests that esterases and not oxidases are responsible for at least some pyrethroid resistance. Elevated esterase activity and its inhibition by TPP were confirmed by native gel electrophoresis. The LC50 estimate obtained for coumaphos in the Panamanian strain was not lowered further than what was observed for susceptible strains by the addition of TPP or PBO. This indicates that enzyme activity might not be involved in coumaphos resistance. Resistance to amitraz was measured through a modification of the Food and Agriculture Organization Larval Packet Test. All tick strains were found to be susceptible to fipronil.

Modifications of exposure time, substrate, and formulation were made to the Food and Agriculture Organization Larval Packet Test (LPT) to determine a combination suitable for measuring the susceptibility of Boophilus microplus (Canestrini) to amitraz. Exposure time influenced the slope of the dose-response when paper was used as a substrate for amitraz. However, time did not influence the dose-response slope when nylon fabric was used as an amitraz substrate. Formulated amitraz produced results with less deviation from the log-probit model than technical amitraz. The combination of formulated amitraz and nylon fabric as a substrate for amitraz produced results that best fit the log-probit model. The modified FAO procedure (formulated amitraz/nylon substrate combination) was used to assay a Brazilian strain of B. microplus and a Panamanian strain of Rhipicephalus sanguineus (Latreille). Resistance ratios (95% CI) of 26.3 (25.7-26.9) and 7.3 (5.5-9.9) were calculated for the B. microplus and R. sanguineus strains, respectively. A discriminating dose of 0.03% amitraz was determined for B. microplus. This technique will help to locate amitraz resistant tick populations, provide data for improved control practices, and aid in the discovery of resistance mechanisms through synergist studies and verification of molecular techniques.

Ticks and the diseases they transmit cause great economic losses to livestock in tropical countries. Non-chemical control alternatives include the use of resistant cattle breeds, biological control and vaccines. However, the most widely used method is the application of different chemical classes of acaricides and macrocyclic lactones. Populations of the cattle tick, Rhipicephalus (Boophilus) microplus, resistant to organophosphates (OP), synthetic pyrethroids (SP), amitraz and fipronil have been reported in Mexico. Macrocyclic lactones are the most sold antiparasitic drug in the Mexican veterinary market. Ivermectin-resistant populations of R. (B.) microplus have been reported in Brazil, Uruguay and especially in Mexico (Veracruz and Yucatan). Although ivermectin resistance levels in R. (B.) microplus from Mexico were generally low in most cases, some field populations of R. (B.) microplus exhibited high levels of ivermectin resistance. The CHPAT population showed a resistance ratio of 10.23 and 79.6 at lethal concentration of 50% and 99%, respectively. Many field populations of R. (B.) microplus are resistant to multiple classes of antiparasitic drugs, including organophosphates (chlorpyrifos, coumaphos and diazinon), pyrethroids (flumethrin, deltamethrin and cypermethrin), amitraz and ivermectin. This paper reports the current status of the resistance of R. (B.) microplus to acaricides, especially ivermectin, in Mexican cattle.

Female Amblyomma maculatum Koch engorged on bovines and were held in the laboratory at 27°C, 70-98% RH, and a photocycle of 12 hr light: 12 hr dark. Thirty-fIve females were disturbed daily by removal of eggs, and 50 others were allowed to oviposit without being disturbed. Weights of females and number of eggs/♀ did not differ significantly in the 2 groups. Average weight of a newly laid egg was 52 μg; that of an egg from an egg mass after oviposition was complete (but before hatching) was 50 µg. For females which were disturbed daily, the number of eggs laid (avg 9963, range 0-17,592) was highly significantly corre!ated with the weight of the female (avg 0.973)g, range 0.390-1.443 g); the regression of number of eggs on weight of females was YD = 10,804 &-548. When females were undisturbed, the number of eggs laid (avg 9130, range 0-18,218) was also highly significantly correlated with weight of the female (avg 0.919 g, range 0.360-1.439 g); the regression was YUD = 13,878 &-3621. An index of reproduction efficiency (no. eggs/wt ♀), established to relate the capacity of the females to produce eggs to their body weight, and an index of conversion efficiency (wt eggs/wt ♀), established to relate the ability of females to convert body weight into egg weight to their body weight, did not differ between the 2 groups and was not correlated with the weight of females. All females showed a highly significant negative correlation of the preoviposition period (avg 4.15 days, range 1-9 days) with the weight of the female. Peak average daily oviposition was 1059 eggs/♀ on the 6th day of oviposition; an average of > 900 eggs/♀ were laid on days 4-8 of oviposition. The length of the oviposition period (avg 18.1 days, range 0-26 days) was highly significantly correlated with the number of eggs but was not correlated with the weight of the female. The average minimum incubation period was 21.9 days (range 19-24 days), and eggs laid during the 1st 2/3 of the oviposition period had a slightly shorter minimum incubation than those laid during the final 1/3 of the oviposition period.

A polymerase chain reaction-based assay was developed to detect the presence of a pyrethroid resistance-associated amino acid substitution in Boophilus microplus (Canestrini). The assay uses a simple method for the extraction of genomic DNA from individual larvae and genotypes individuals for the presence of a Phe-->Ile amino acid substitution in the S6 transmembrane segment of domain III of the para-like sodium channel, clearly distinguishing heterozygotes from homozygotes. High frequencies for this amino acid substitution were found in the Corrales and San Felipe strains, which have target site insensitivity mechanisms for pyrethroid resistance. The Caporal resistant strain contained lower yet substantial numbers of amino acid-substituted alleles. Low amino acid substitution frequencies were found in the susceptible reference Gonzales strain and the Coatzacoalcos strain, which has metabolic esterase-mediated pyrethroid resistance. The amino acid substitution was not found in six other strains that were susceptible to pyrethroids.

ABSTRACT' BACKGROUND: For >100 years cattle production in the southern United States has been threatened by cattle fever. It is caused by an invasive parasite-vector complex that includes the protozoan hemoparasites Babesia bovis and B. bigemina, which are transmitted among domestic cattle via Rhipicephalus tick vectors of the subgenus Boophilus. In 1906 an eradication effort was started and by 1943 Boophilus ticks had been confined to a narrow tick eradication quarantine area (TEQA) along the Texas-Mexico border. However, a dramatic increase in tick infestations in areas outside the TEQA over the last decade suggests these tick vectors may be poised to re-invade the southern United States. We investigated historical and potential future distributions of climatic habitats of cattle fever ticks to assess the potential for a range expansion. METHODS: We built robust spatial predictions of habitat suitability for the vector species Rhipicephalus (Boophilus) microplus and R. (B.) annulatus across the southern United States for three time periods: 1906, present day (2012), and 2050. We used analysis of molecular variance (AMOVA) to identify persistent tick occurrences and analysis of bias in the climate proximate to these occurrences to identify key environmental parameters associated with the ecology of both species. We then used ecological niche modeling algorithms GARP and Maxent to construct models that related known occurrences of ticks in the TEQA during 2001-2011 with geospatial data layers that summarized important climate parameters at all three time periods. RESULTS: We identified persistent tick infestations and specific climate parameters that appear to be drivers of ecological niches of the two tick species. Spatial models projected onto climate data representative of climate in 1906 reproduced historical pre-eradication tick distributions. Present-day predictions, although constrained to areas near the TEQA, extrapolated well onto climate projections for 2050. CONCLUSIONS: Our models indicate the potential for range expansion of climate suitable for survival of R. microplus and R. annulatus in the southern United States by mid-century, which increases the risk of reintroduction of these ticks and cattle tick fever into major cattle producing areas.

BACKGROUND: Rhipicephalus (Boophilus) microplus is a highly-invasive tick that transmits the cattle parasites (Babesia bovis and B. bigemina) that cause cattle fever. R. microplus and Babesia are endemic in Mexico and ticks persist in the United States inside a narrow tick eradication quarantine area (TEQA) along the Rio Grande. This containment area is threatened by unregulated movements of illegal cattle and wildlife like white-tailed deer (WTD; Odocoileus virginianus). METHODS: Using 11 microsatellite loci we genotyped 1,247 R. microplus from 63 Texas collections, including outbreak infestations from outside the TEQA. We used population genetic analyses to test hypotheses about ecological persistence, tick movement, and impacts of the eradication program in southern Texas. We tested acaricide resistance with larval packet tests (LPTs) on 47 collections. RESULTS: LPTs revealed acaricide resistance in 15/47 collections (32%); 11 were outside the TEQA and three were resistant to multiple acaricides. Some collections highly resistant to permethrin were found on cattle and WTD. Analysis of genetic differentiation over time at seven properties revealed local gene pools with very low levels of differentiation (FST 0.00-0.05), indicating persistence over timespans of up to 29 months. However, in one neighborhood differentiation varied greatly over a 12-month period (FST 0.03-0.13), suggesting recurring immigration from distinct sources as another persistence mechanism. Ticks collected from cattle and WTD at the same location are not differentiated (FST = 0), implicating ticks from WTD as a source of ticks on cattle (and vice versa) and emphasizing the importance of WTD to tick control strategies. We identified four major genetic groups (K = 4) using Bayesian population assignment, suggesting multiple introductions to Texas. CONCLUSIONS: Two dispersal mechanisms give rise to new tick infestations: 1) frequent short-distance dispersal from the TEQA; and 2) rare long-distance, human-mediated dispersal from populations outside our study area, probably Mexico. The threat of cattle fever tick transport into Texas is increased by acaricide resistance and the ability of R. microplus to utilize WTD as an alternate host. Population genetic analyses may provide a powerful tool for tracking invasions in other parts of the world where these ticks are established.