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Xu B, Gu M, Wu Q, Shu C, Tan W, Wang S, Zhong Z, Wang X, Li J, Wang J, Wang Y, Hu W. The bacterial patterns suggesting the dynamic features of tick-associated microorganisms in hard ticks. BMC Microbiol 2024; 24:179. [PMID: 38789934 PMCID: PMC11118998 DOI: 10.1186/s12866-024-03323-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 05/06/2024] [Indexed: 05/26/2024] Open
Abstract
BACKGROUND Ticks are blood-feeding significant arthropods that can harbour various microorganisms, including pathogens that pose health risks to humans and animals. Tick-symbiont microorganisms are believed to influence tick development, but the intricate interactions between these microbes and the relationships between different tick-borne microorganisms remain largely unexplored. RESULTS Based on 111 tick pool samples presenting questing and engorged statuses including 752 questing tick and 1083 engorged tick from cattle and goats, which were collected in two types of geographic landscape (semi-desert and alpine meadow). We observed significant variations in the composition of tick-borne microorganisms across different environments and blood-engorgement statuses, with a pronounced divergence in symbionts compared to environmental bacteria. Metabolic predictions revealed over 90 differential pathways for tick-borne microorganisms in distinct environments and more than 80 metabolic variations in response to varying blood engorgement statuses. Interestingly, nine pathways were identified, particularly related to chorismate synthesis and carbohydrate metabolism. Moreover, microbial network relationships within tick-borne microorganism groups were highly distinct across different environments and blood-engorgement statuses. The microbial network relationships of symbionts involve some pathogenic and environmental microorganisms. Regression modelling highlighted positive correlations between the Coxiella symbiont and related pathogens, while some environmental bacteria showed strong negative correlations with Coxiella abundance. We also identified commensal bacteria/pathogens in bacterial cooccurrence patterns. Furthermore, we tested pathogenic microorganisms of each tick sample analysis revealed that 86.36% (1601/1855) of the tick samples carried one or more pathogenic microorganisms, The total carrier rate of bacterial pathogens was 43.77% ((812/1855). Most blood samples carried at least one pathogenic microorganism. The pathogens carried by the ticks have both genus and species diversity, and Rickettsia species are the most abundant pathogens among all pathogens. CONCLUSION Our findings underscore that the bacterial pattern of ticks is dynamic and unstable, which is influenced by the environment factors and tick developmental characteristics.
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Affiliation(s)
- Bin Xu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Chinese Center for Tropical Diseases Research, Shanghai, China
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention (Chinese Center for Tropical Diseases Research), National Health Commission Key Laboratory of Parasite and Vector Biology, WHO Collaborating Center for Tropical Diseases, National Center for International Research on Tropical Diseases, Shanghai, China
| | - Mengjie Gu
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Qunfeng Wu
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Chang Shu
- Key Laboratory for Prevention and Control of Emerging Infectious Diseases and Public Health Security of the XPCC, School of Medicine, Shihezi University, Shihezi City, Xinjiang Uygur Autonomous Region, China
- Hainan Medical University, Haikou, China
| | - Wenbo Tan
- Key Laboratory for Prevention and Control of Emerging Infectious Diseases and Public Health Security of the XPCC, School of Medicine, Shihezi University, Shihezi City, Xinjiang Uygur Autonomous Region, China
| | - Suwen Wang
- Key Laboratory for Prevention and Control of Emerging Infectious Diseases and Public Health Security of the XPCC, School of Medicine, Shihezi University, Shihezi City, Xinjiang Uygur Autonomous Region, China
| | - Zhengwei Zhong
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Xiaoling Wang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Jian Li
- Basic Medical College, Guangxi University of Chinese Medicine, Guangxi, Nanning, China
| | - Jingwen Wang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Yuanzhi Wang
- Key Laboratory for Prevention and Control of Emerging Infectious Diseases and Public Health Security of the XPCC, School of Medicine, Shihezi University, Shihezi City, Xinjiang Uygur Autonomous Region, China.
| | - Wei Hu
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention (Chinese Center for Tropical Diseases Research), National Health Commission Key Laboratory of Parasite and Vector Biology, WHO Collaborating Center for Tropical Diseases, National Center for International Research on Tropical Diseases, Shanghai, China.
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China.
- The institutes of Biomedical Sciences, College of Life Sciences, Inner Mongolia University, Inner Mongolia, Hohhot, China.
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Yin F, Guo C, Li D, Tian Z, Li F. Molecular Survey and Genetic Characteristics of Vector-Borne Pathogens in Domestic Dogs from Four Regions of China. Animals (Basel) 2023; 13:1867. [PMID: 37889788 PMCID: PMC10251890 DOI: 10.3390/ani13111867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 05/27/2023] [Accepted: 05/31/2023] [Indexed: 10/29/2023] Open
Abstract
Canine vector-borne diseases are widely distributed around the world. They are transmitted by arthropods, and many seriously threaten the health of animals and humans. In China, our knowledge of Ehrlichia, Hepatozoon, and Mycoplasma species circulating in dogs is still poorly understood. Therefore, the aim of this study was to understand the prevalence and genetic characteristics of canine Ehrlichia spp., Hepatozoon spp., and Mycoplasma spp. in Chongqing (southwest), Fujian (southeast), Shandong (southeast), and Hubei (central) Provinces of China. Blood samples from healthy pet dogs were processed to detect Ehrlichia, Hepatozoon, and Mycoplasma DNA with PCR. Haplotype and phylogenetic analyses were performed on 18S rRNA sequences. Among 306 dogs, no Ehrlichia spp. or Mycoplasma spp. were detected, whereas one Hepatozoon sp. was detected in 10 (3.27%) of the animals. Only Hepatozoon canis was identified and was endemic to Chongqing (2.46%) and Hubei (8.77%). A haplotype analysis identified eight haplotypes among the H. canis isolates. A phylogenetic analysis showed that the H. canis isolates in this study clustered into four clades, together with isolates from different countries and hosts, forming a large group that was clearly separate from other Hepatozoon species. These findings provided new information on the epidemiological characteristics of canine vector-borne diseases in China and will be helpful in the development of efficient measures to safeguard the health and well-being of companion animals and their owners.
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Affiliation(s)
| | | | | | | | - Facai Li
- College of Veterinary Medicine, Southwest University, Chongqing 400715, China
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Trout Fryxell RT, Vann DN, Butler RA, Paulsen DJ, Chandler JG, Willis MP, Wyrosdick HM, Schaefer JJ, Gerhold RW, Grove DM, Ivey JZ, Thompson KW, Applegate RD, Sweaney J, Daniels S, Beaty S, Balthaser D, Freye JD, Mertins JW, Bonilla DL, Lahmers K. Rapid Discovery and Detection of Haemaphysalis longicornis through the Use of Passive Surveillance and Collaboration: Building a State Tick-Surveillance Network. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:7980. [PMID: 34360274 PMCID: PMC8345789 DOI: 10.3390/ijerph18157980] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 07/23/2021] [Indexed: 01/21/2023]
Abstract
Between March 2019 and February 2020, Asian long-horned ticks (Haemaphysalis longicornis Neumann, 1901) were discovered and collected for the first time in one middle and seven eastern Tennessee counties, facilitated by a newly developed passive and collaborative tick-surveillance network. Network collaborators included federal, state, county, university, and private resource personnel working with companion animals, livestock, and wildlife. Specimens were collected primarily from dogs and cattle, with initial detections of female adult stage ticks by stakeholders associated with parasitology positions (e.g., entomologists and veterinary parasitologists). Initial county tick detections were confirmed with morphological and molecular identifications, and then screened for the presence of animal-associated pathogens (Anaplasma marginale, Babesia species, Ehrlichia species, and Theileria orientalis), for which all tests were negative. Herein, we describe the identification and confirmation of these tick specimens as well as other results of the surveillance collaboration.
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Affiliation(s)
- Rebecca T. Trout Fryxell
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (R.A.B.); (D.J.P.); (J.G.C.)
| | - Dené N. Vann
- Department of Biomedical Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA; (D.N.V.); (H.M.W.); (J.J.S.); (R.W.G.)
| | - Rebecca A. Butler
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (R.A.B.); (D.J.P.); (J.G.C.)
| | - Dave J. Paulsen
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (R.A.B.); (D.J.P.); (J.G.C.)
| | - Jennifer G. Chandler
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (R.A.B.); (D.J.P.); (J.G.C.)
| | - Micah P. Willis
- Department of Agricultural Leadership, Education and Communications, University of Tennessee, Knoxville, TN 37996, USA;
| | - Heidi M. Wyrosdick
- Department of Biomedical Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA; (D.N.V.); (H.M.W.); (J.J.S.); (R.W.G.)
| | - John J. Schaefer
- Department of Biomedical Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA; (D.N.V.); (H.M.W.); (J.J.S.); (R.W.G.)
| | - Richard W. Gerhold
- Department of Biomedical Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA; (D.N.V.); (H.M.W.); (J.J.S.); (R.W.G.)
| | - Daniel M. Grove
- Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN 37996, USA;
| | - Jennie Z. Ivey
- Department of Animal Science, University of Tennessee, Knoxville, TN 37996, USA;
| | - Kevin W. Thompson
- Middle Tennessee Research and Education Center, University of Tennessee, Knoxville, TN 37996, USA;
| | - Roger D. Applegate
- Wildlife and Forestry Division, Tennessee Wildlife Resources Agency, Nashville, TN 37211, USA; (R.D.A.); (J.S.); (S.D.)
| | - Joy Sweaney
- Wildlife and Forestry Division, Tennessee Wildlife Resources Agency, Nashville, TN 37211, USA; (R.D.A.); (J.S.); (S.D.)
| | - Sterling Daniels
- Wildlife and Forestry Division, Tennessee Wildlife Resources Agency, Nashville, TN 37211, USA; (R.D.A.); (J.S.); (S.D.)
| | - Samantha Beaty
- State Veterinarians’ Office, Ellington Agricultural Center, Tennessee Department of Agriculture, Nashville, TN 37220, USA; (S.B.); (D.B.)
| | - Douglas Balthaser
- State Veterinarians’ Office, Ellington Agricultural Center, Tennessee Department of Agriculture, Nashville, TN 37220, USA; (S.B.); (D.B.)
| | - James D. Freye
- Tennessee Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Madison, TN 37220, USA;
| | - James W. Mertins
- National Veterinary Services Laboratories, Veterinary Services, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA 50010, USA;
| | - Denise L. Bonilla
- Veterinary Services, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Fort Collins, CO 80521, USA;
| | - Kevin Lahmers
- Virginia Tech Animal Laboratory Services and Department of Biomedical Sciences and Pathobiology, VA Polytechnic Institute and State University, Blacksburg, VA 24061, USA;
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Ghauri HN, Ijaz M, Ahmed A, Muhammad Naveed MUA, Nawab Y, Javed MU, Ghaffar A. MOLECULAR INVESTIGATION AND PHYLOGENETIC ANALYSIS OF ANAPLASMOSIS IN DOGS. J Parasitol 2021; 107:295-303. [PMID: 33844841 DOI: 10.1645/20-50] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Anaplasmosis is a widespread vector-borne disease affecting dogs, and Anaplasma platys is the major etiological agent of the disease. The study examines anaplasmosis molecular prevalence, related risk factors, and alteration of hematological variables in Anaplasma-affected dogs. A total of 150 blood samples were collected from dogs in the district of Lahore, Pakistan. The samples were screened with PCR targeting the 16S rRNA gene of Anaplasma. Sequencing of samples that were found positive after performing PCR was conducted. A questionnaire was developed to collect epidemiological data on subject dogs, and the information was analyzed with a logistic regression model using SPSS. The current study revealed an 11.34% (17/150) prevalence of anaplasmosis in dogs based on PCR detection. Tick infestation, previous tick history, house hygiene, and tick control status were major risk factors linked with disease occurrence. Red blood cell count, packed cell volume, hemoglobin, and platelet count were decreased significantly (P < 0.05) in Anaplasma-infected dogs. Phylogenetically, the 2 isolates of the current study clustered together, and that cluster was very similar to A. platys isolates from India, Malaysia, and Thailand.
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Affiliation(s)
- Hammad Nayyar Ghauri
- Department of Clinical Medicine and Surgery University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Muhammad Ijaz
- Department of Clinical Medicine and Surgery University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Arslan Ahmed
- Department of Clinical Medicine and Surgery University of Veterinary and Animal Sciences, Lahore, Pakistan
| | | | - Yasir Nawab
- Department of Clinical Medicine and Surgery University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Muhammad Umar Javed
- Department of Clinical Medicine and Surgery University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Awais Ghaffar
- Department of Clinical Medicine and Surgery University of Veterinary and Animal Sciences, Lahore, Pakistan
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Díaz-Sánchez AA, Hofmann-Lehmann R, Meli ML, Roblejo-Arias L, Fonseca-Rodríguez O, Castillo AP, Cañizares EV, Rivero EL, Chilton NB, Corona-González B. Molecular detection and characterization of Hepatozoon canis in stray dogs from Cuba. Parasitol Int 2020; 80:102200. [PMID: 32980550 DOI: 10.1016/j.parint.2020.102200] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/09/2020] [Accepted: 07/15/2020] [Indexed: 11/25/2022]
Abstract
Canine hepatozoonosis caused by Hepatozoon canis is a worldwide distributed tick-borne disease of domestic and wild canids that is transmitted by ingestion of Rhipicephalus sanguineus sensu lato (s.l.) ticks. The present study was aimed to determine the prevalence of Hepatozoon infections in 80 stray dogs from Havana Province in Cuba, and to confirm the species identity and phylogenetic relationships of the causative agent. Samples were screened by microscopical examination of thin blood smears for the presence of Hepatozoon spp. gamonts and by genus-specific SYBR green-based real-time PCR assay targeting the 18S rRNA gene. Direct microscopy examination revealed Hepatozoon gamonts in the peripheral blood of 8 dogs (10.0%; 95% CI: 4.80-18.0%), while 38 animals (47.5%; 95% CI: 36.8-58.4%) were PCR-positive, including all microscopically positive dogs. Hence, the agreement between the two detection methods was 'poor' (κ = 0.20). Hematological parameters did not differ significantly between PCR-positive and PCR-negative dogs (p > 0.05). The DNA sequences of the 18S rRNA gene of the Hepatozoon spp. from Cuban dogs showed a nucleotide identity >99% with those of 18S rRNA sequences of Hepatozoon canis isolates from Czech Republic, Brazil and Spain. Phylogenetic analysis revealed that obtained sequences clustered within the Hepatozoon canis clade, different from the Hepatozoon felis or Hepatozoon americanum clades. The present study represents the first molecular characterization of Hepatozoon canis in stray dogs within Cuba.
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Affiliation(s)
- Adrian Alberto Díaz-Sánchez
- Centro Nacional de Sanidad Agropecuaria (CENSA), Carretera de Tapaste y Autopista Nacional, Apartado postal 10, 32700 San José de las Lajas, Mayabeque, Cuba; Clinical Laboratory, Department of Clinical Diagnostics and Services, and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland; Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Regina Hofmann-Lehmann
- Clinical Laboratory, Department of Clinical Diagnostics and Services, and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Marina L Meli
- Clinical Laboratory, Department of Clinical Diagnostics and Services, and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Lisset Roblejo-Arias
- Centro Nacional de Sanidad Agropecuaria (CENSA), Carretera de Tapaste y Autopista Nacional, Apartado postal 10, 32700 San José de las Lajas, Mayabeque, Cuba
| | | | - Anisleidy Pérez Castillo
- Centro Nacional de Sanidad Agropecuaria (CENSA), Carretera de Tapaste y Autopista Nacional, Apartado postal 10, 32700 San José de las Lajas, Mayabeque, Cuba
| | - Ernesto Vega Cañizares
- Centro Nacional de Sanidad Agropecuaria (CENSA), Carretera de Tapaste y Autopista Nacional, Apartado postal 10, 32700 San José de las Lajas, Mayabeque, Cuba
| | - Evelyn Lobo Rivero
- Centro Nacional de Sanidad Agropecuaria (CENSA), Carretera de Tapaste y Autopista Nacional, Apartado postal 10, 32700 San José de las Lajas, Mayabeque, Cuba
| | - Neil B Chilton
- Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Belkis Corona-González
- Centro Nacional de Sanidad Agropecuaria (CENSA), Carretera de Tapaste y Autopista Nacional, Apartado postal 10, 32700 San José de las Lajas, Mayabeque, Cuba.
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Drake J, Parrish R. Dog importation and changes in canine intestinal nematode prevalence in Colorado, USA, 2013-2017. Parasit Vectors 2020; 13:404. [PMID: 32771048 PMCID: PMC7414742 DOI: 10.1186/s13071-020-04283-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 08/03/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Animal rescue and animal welfare organizations are relocating thousands of dogs per year following natural disasters and in attempts to provide greater adoption opportunities. Many dogs are sourced from the southeastern USA, which historically has a high prevalence rate for many parasites and parasitic diseases. The Colorado Department of Agriculture Pet Animal Care Facilities Act (PACFA) requires animal shelters and animal welfare organizations to report annually a variety of statistics including the numbers of dogs imported into Colorado from out of state. The Companion Animal Parasite Council (CAPC) provides data nationally, down to the state and county level, on a variety of common parasitic and vector borne diseases. These data make it possible to track changes in parasite prevalence over several years. METHODS Test results for canine roundworm, hookworm and whipworm were collected from the CAPC maps for 2013-2017. Dog importation data for 2014-2017 was collected from PACFA reports. For evaluation of the statistical significance of prevalence changes when comparing 2013 to 2017, 2 × 2 contingency tables were constructed with both positive and negative test results for each year and the data assessed using Chi-square tests to determine if the 2017 prevalence was significantly different than the 2013 prevalence for roundworm, hookworm and whipworm. RESULTS Significant increases in intestinal nematode prevalence occurred in Colorado from 2013 to 2017. The prevalence of canine roundworm rose 35.60%, the prevalence of canine hookworm rose 137.33% and the prevalence of canine whipworm rose 63.68%. From 2014 to 2017, over 114,000 dogs were transported into Colorado from out-of-state, by more than 130 animal shelters and rescue organizations. Three of the larger organizations reported that the majority of their dogs were obtained from New Mexico, Texas and Oklahoma. Texas and Oklahoma have historically much higher parasite prevalence than Colorado. CONCLUSIONS Veterinarians in areas with historically low parasite prevalence where dogs from high parasite prevalence areas are arriving for adoption may need to reevaluate their recommendations regarding fecal examination and deworming frequencies as historic levels of intestinal parasite infection may no longer be accurate assessments of future infection risks.
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Affiliation(s)
- Jason Drake
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN, 46140, USA.
| | - Rudolph Parrish
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN, 46140, USA
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Lashnits EW, Dawson DE, Breitschwerdt E, Lanzas C. Ecological and Socioeconomic Factors Associated with Bartonella henselae Exposure in Dogs Tested for Vector-Borne Diseases in North Carolina. Vector Borne Zoonotic Dis 2019; 19:582-595. [PMID: 31112095 PMCID: PMC6685192 DOI: 10.1089/vbz.2018.2397] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Bartonella henselae is a zoonotic vector-borne pathogen affecting both humans and dogs. Little is known about the epidemiology of B. henselae in dogs, including risk factors associated with exposure. The objectives of this study were to map the current distribution of B. henselae in dogs in North Carolina (NC) and to identify ecological and socioeconomic factors influencing B. henselae seroreactivity. Results from 4446 B. henselae serology samples from dogs in NC submitted by veterinarians for clinical diagnostic testing to the North Carolina State University College of Veterinary Medicine Vector Borne Disease Diagnostic Laboratory between January 1, 2004 and December 31, 2015 were retrospectively reviewed. These results were used to generate a map of B. henselae seroreactivity. To account for sparsely sampled areas, statistical smoothing using head banging and areal interpolation kriging was performed. Using previously described risk factors for exposure to canine tick-borne diseases, eight multivariable logistic regression models based on biologically plausible hypotheses were tested, and a final model was selected using an Akaike's Information Criterion weighted-average approach. Seroreactivity among dogs tested for vector-borne disease was variable across the state: higher along the southern/eastern coastal plains and eastern Piedmont, and lower in the western mountains. Of 25 explanatory factors considered, the model combining demographic, socioeconomic, climatic, and land use variables fits best. Based on this model, female intact sex and increasing percentage of the county with low-intensity development and evergreen forest were associated with higher seroreactivity. Conversely, moderate development, increasing median household income, and higher temperature range and relative humidity were associated with lower seroreactivity. This model could be improved, however, by including local and host-scale factors that may play a significant role in dogs' exposure.
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Affiliation(s)
- Erin W. Lashnits
- Comparative Biomedical Sciences Graduate Program, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Daniel E. Dawson
- Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Edward Breitschwerdt
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Cristina Lanzas
- Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
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Prevalence, molecular characterization and risk factor analysis of Ehrlichia canis and Anaplasma platys in domestic dogs from Paraguay. Comp Immunol Microbiol Infect Dis 2019; 62:31-39. [DOI: 10.1016/j.cimid.2018.11.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 11/21/2018] [Accepted: 11/27/2018] [Indexed: 11/18/2022]
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Cabezas-Cruz A, Allain E, Ahmad AS, Saeed MA, Rashid I, Ashraf K, Yousfi L, Shehzad W, Indjein L, Rodriguez-Valle M, Estrada-Peña A, Obregón D, Jabbar A, Moutailler S. Low genetic diversity of Ehrlichia canis associated with high co-infection rates in Rhipicephalus sanguineus (s.l.). Parasit Vectors 2019; 12:12. [PMID: 30616670 PMCID: PMC6322249 DOI: 10.1186/s13071-018-3194-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 11/09/2018] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Rhipicephalus sanguineus sensu lato (s.l.) is the most widely distributed ixodid tick and is a vector of major canine and human pathogens. High-throughput technologies have revealed that individual ticks carry a high diversity of pathogens, including bacteria, protozoa and viruses. Currently, it is accepted that co-infections (multiple pathogen species within an individual) are very common in ticks and influence pathogen acquisition and transmission as well as host infection risk. However, little is known on the impact of the genetic diversity of pathogens on the incidence of co-infections. Herein, we studied the frequency of co-infections in R. sanguineus (s.l.) and their association with the genetic diversity of Ehrlichia canis. METHODS Rhipicephalus sanguineus (s.l.) female ticks (n = 235) were collected from healthy farm dogs in three districts of Pakistan. Microfluidic real-time PCR, a powerful nanotechnology for high-throughput molecular detection of pathogens, was used to test the presence of 25 bacterial and seven parasitic species in individual ticks. The genetic diversity of E. canis was evaluated by characterizing the trp36 gene. RESULTS A total of 204 ticks were infected with at least one pathogen and 109 co-infected with two (80%) or three (20%) pathogens. Rickettsia massiliae (human pathogen) and E. canis (zoonotic dog pathogen) were the most common pathogens co-infecting (30.4%) ticks. Furthermore, all identified co-infections included R. massiliae and/or E. canis. Multiple correspondence analysis (MCA) revealed that single infections did not show clear regional association whereas some co-infections were restricted to certain geographical regions. The sequence analysis of trp36 in representative samples allowed the identification of three E. canis strains with low genetic diversity, and the strain found in Muzaffargarh district appeared to be more adapted to co-infection with R. massiliae. CONCLUSIONS Rhipicephalus sanguineus (s.l.) harbors multiple co-infections with human and dog pathogens of zoonotic potential. Findings of this study suggest that genetic diversity of E. canis may favor co-infections with different pathogens.
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Affiliation(s)
- Alejandro Cabezas-Cruz
- UMR BIPAR, INRA, ANSES, Ecole Nationale Vétérinaire d’Alfort, Université Paris-Est, 94700 Maisons-Alfort, France
| | - Eleonore Allain
- UMR BIPAR, INRA, ANSES, Ecole Nationale Vétérinaire d’Alfort, Université Paris-Est, 94700 Maisons-Alfort, France
| | - Abdullah S. Ahmad
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Victoria 3030 Australia
- Department of Parasitology, Faculty of Veterinary Sciences, University of Veterinary and Animal Sciences, Lahore, Punjab Pakistan
| | - Muhammad A. Saeed
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Victoria 3030 Australia
| | - Imran Rashid
- Department of Parasitology, Faculty of Veterinary Sciences, University of Veterinary and Animal Sciences, Lahore, Punjab Pakistan
| | - Kamran Ashraf
- Department of Parasitology, Faculty of Veterinary Sciences, University of Veterinary and Animal Sciences, Lahore, Punjab Pakistan
| | - Lena Yousfi
- UMR BIPAR, INRA, ANSES, Ecole Nationale Vétérinaire d’Alfort, Université Paris-Est, 94700 Maisons-Alfort, France
| | - Wasim Shehzad
- Institute of Biochemistry and Biotechnology, Faculty of Biosciences, University of Veterinary and Animal Sciences, Lahore, Punjab Pakistan
| | - Lea Indjein
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Victoria 3030 Australia
| | - Manuel Rodriguez-Valle
- Queensland Alliance for Agriculture & Food Innovation, The University of Queensland, St. Lucia, Queensland 4072 Australia
| | | | - Dasiel Obregón
- Cell and Molecular Biology Laboratory, Center for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, SP Brazil
| | - Abdul Jabbar
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Victoria 3030 Australia
| | - Sara Moutailler
- UMR BIPAR, INRA, ANSES, Ecole Nationale Vétérinaire d’Alfort, Université Paris-Est, 94700 Maisons-Alfort, France
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10
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Ahmad AS, Saeed MA, Rashid I, Ashraf K, Shehzad W, Traub RJ, Baneth G, Jabbar A. Molecular characterization of Hepatozoon canis from farm dogs in Pakistan. Parasitol Res 2018; 117:1131-1138. [PMID: 29455420 DOI: 10.1007/s00436-018-5790-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 01/25/2018] [Indexed: 11/29/2022]
Abstract
Hepatozoon canis is a tick-borne pathogen of canids, which is distributed worldwide. However, very little is known about this protozoan parasite in Pakistan. This study provides the first molecular evidence of H. canis from farm dogs from three agro-ecological zones of Punjab, Pakistan. A conventional PCR targeting the 18S rRNA gene was used to characterize H. canis from farm dogs from three districts, namely Kasur, Rawalpindi, and Muzaffargarh, in Punjab. Of 341 blood samples tested, 155 (45.5%) were positive for H. canis, 73 (61.3%) from Kasur, 46 (42.5%) from Rawalpindi, and 36 (31.5%) from Muzaffargarh. Phylogenetic analyses revealed that 18S rRNA sequences of H. canis from this study clustered in three clades with those of H. canis from previously published studies to the exclusion of all other Hepatozoon spp. included in the analysis. This study provides the first insight into H. canis from farm dogs in Pakistan. Furthermore, it lays a foundation for future studies of the parasite to assess the impact of canine hepatozoonosis in dogs from various agro-ecological zones in Pakistan where pet ownership of dogs is increasing.
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Affiliation(s)
- Abdullah S Ahmad
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Melbourne, Victoria, Australia.,Department of Parasitology, Faculty of Veterinary Sciences, University of Veterinary and Animal Sciences, Lahore, Punjab, Pakistan
| | - Muhammad A Saeed
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Melbourne, Victoria, Australia
| | - Imran Rashid
- Department of Parasitology, Faculty of Veterinary Sciences, University of Veterinary and Animal Sciences, Lahore, Punjab, Pakistan
| | - Kamran Ashraf
- Department of Parasitology, Faculty of Veterinary Sciences, University of Veterinary and Animal Sciences, Lahore, Punjab, Pakistan
| | - Wasim Shehzad
- Institute of Biochemistry and Biotechnology, Faculty of Biosciences, University of Veterinary and Animal Sciences, Lahore, Punjab, Pakistan
| | - Rebecca J Traub
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Melbourne, Victoria, Australia
| | - Gad Baneth
- The Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Abdul Jabbar
- Department of Veterinary Biosciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Melbourne, Victoria, Australia.
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11
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Estrada-Peña A, Roura X, Sainz A, Miró G, Solano-Gallego L. Species of ticks and carried pathogens in owned dogs in Spain: Results of a one-year national survey. Ticks Tick Borne Dis 2017; 8:443-452. [DOI: 10.1016/j.ttbdis.2017.02.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 01/31/2017] [Accepted: 02/01/2017] [Indexed: 10/20/2022]
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12
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Watson SC, Liu Y, Lund RB, Gettings JR, Nordone SK, McMahan CS, Yabsley MJ. A Bayesian spatio-temporal model for forecasting the prevalence of antibodies to Borrelia burgdorferi, causative agent of Lyme disease, in domestic dogs within the contiguous United States. PLoS One 2017; 12:e0174428. [PMID: 28472096 PMCID: PMC5417420 DOI: 10.1371/journal.pone.0174428] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 03/08/2017] [Indexed: 01/12/2023] Open
Abstract
This paper models the prevalence of antibodies to Borrelia burgdorferi in domestic dogs in the United States using climate, geographic, and societal factors. We then use this model to forecast the prevalence of antibodies to B. burgdorferi in dogs for 2016. The data available for this study consists of 11,937,925 B. burgdorferi serologic test results collected at the county level within the 48 contiguous United States from 2011-2015. Using the serologic data, a baseline B. burgdorferi antibody prevalence map was constructed through the use of spatial smoothing techniques after temporal aggregation; i.e., head-banging and Kriging. In addition, several covariates purported to be associated with B. burgdorferi prevalence were collected on the same spatio-temporal granularity, and include forestation, elevation, water coverage, temperature, relative humidity, precipitation, population density, and median household income. A Bayesian spatio-temporal conditional autoregressive (CAR) model was used to analyze these data, for the purposes of identifying significant risk factors and for constructing disease forecasts. The fidelity of the forecasting technique was assessed using historical data, and a Lyme disease forecast for dogs in 2016 was constructed. The correlation between the county level model and baseline B. burgdorferi antibody prevalence estimates from 2011 to 2015 is 0.894, illustrating that the Bayesian spatio-temporal CAR model provides a good fit to these data. The fidelity of the forecasting technique was assessed in the usual fashion; i.e., the 2011-2014 data was used to forecast the 2015 county level prevalence, with comparisons between observed and predicted being made. The weighted (to acknowledge sample size) correlation between 2015 county level observed prevalence and 2015 forecasted prevalence is 0.978. A forecast for the prevalence of B. burgdorferi antibodies in domestic dogs in 2016 is also provided. The forecast presented from this model can be used to alert veterinarians in areas likely to see above average B. burgdorferi antibody prevalence in dogs in the upcoming year. In addition, because dogs and humans can be exposed to ticks in similar habitats, these data may ultimately prove useful in predicting areas where human Lyme disease risk may emerge.
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Affiliation(s)
- Stella C. Watson
- Department of Mathematical Sciences, Clemson University, Clemson, SC, United States of America
| | - Yan Liu
- Department of Mathematical Sciences, Clemson University, Clemson, SC, United States of America
| | - Robert B. Lund
- Department of Mathematical Sciences, Clemson University, Clemson, SC, United States of America
| | - Jenna R. Gettings
- Department of Mathematical Sciences, Clemson University, Clemson, SC, United States of America
| | - Shila K. Nordone
- Department of Molecular and Biomedical Sciences, Comparative Medicine Institute, North Carolina State University, College of Veterinary Medicine, Raleigh, NC, United States of America
| | - Christopher S. McMahan
- Department of Mathematical Sciences, Clemson University, Clemson, SC, United States of America
| | - Michael J. Yabsley
- Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, United States of America
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13
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Liu Y, Lund RB, Nordone SK, Yabsley MJ, McMahan CS. A Bayesian spatio-temporal model for forecasting the prevalence of antibodies to Ehrlichia species in domestic dogs within the contiguous United States. Parasit Vectors 2017; 10:138. [PMID: 28274248 PMCID: PMC5343545 DOI: 10.1186/s13071-017-2068-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 02/27/2017] [Indexed: 11/30/2022] Open
Abstract
Background Dogs in the United States are hosts to a diverse range of vector-borne pathogens, several of which are important zoonoses. This paper describes factors deemed to be significantly related to the prevalence of antibodies to Ehrlichia spp. in domestic dogs, including climatic conditions, geographical factors, and societal factors. These factors are used in concert with a spatio-temporal model to construct an annual seroprevalence forecast. The proposed method of forecasting and an assessment of its fidelity are described. Methods Approximately twelve million serological test results for canine exposure to Ehrlichia spp. were used in the development of a Bayesian approach to forecast canine infection. Data used were collected on the county level across the contiguous United States from routine veterinary diagnostic tests between 2011–2015. Maps depicting the spatial baseline Ehrlichia spp. prevalence were constructed using Kriging and head-banging smoothing methods. Data were statistically analyzed to identify factors related to antibody prevalence via a Bayesian spatio-temporal conditional autoregressive (CAR) model. Finally, a forecast of future Ehrlichia seroprevalence was constructed based on the proposed model using county-level data on five predictive factors identified at a workshop hosted by the Companion Animal Parasite Council and published in 2014: annual temperature, percentage forest coverage, percentage surface water coverage, population density and median household income. Data were statistically analyzed to identify factors related to disease prevalence via a Bayesian spatio-temporal model. The fitted model and factor extrapolations were then used to forecast the regional seroprevalence for 2016. Results The correlation between the observed and model-estimated county-by-county Ehrlichia seroprevalence for the five-year period 2011–2015 is 0.842, demonstrating reasonable model accuracy. The weighted correlation (acknowledging unequal sample sizes) between 2015 observed and forecasted county-by-county Ehrlichia seroprevalence is 0.970, demonstrating that Ehrlichia seroprevalence can be forecasted accurately. Conclusions The forecast presented herein can be an a priori alert to veterinarians regarding areas expected to see expansion of Ehrlichia beyond the accepted endemic range, or in some regions a dynamic change from historical average prevalence. Moreover, this forecast could potentially serve as a surveillance tool for human health and prove useful for forecasting other vector-borne diseases.
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Affiliation(s)
- Yan Liu
- Department of Mathematical Sciences, Clemson University, Clemson, SC, USA
| | - Robert B Lund
- Department of Mathematical Sciences, Clemson University, Clemson, SC, USA
| | - Shila K Nordone
- Department of Molecular and Biomedical Sciences, Comparative Medicine Institute, North Carolina State University, Raleigh, NC, USA
| | - Michael J Yabsley
- Department of Population Health, Southeastern Cooperative Wildlife Disease Study, College of Veterinary Medicine and the Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA, USA.
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14
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Bowman DD, Liu Y, McMahan CS, Nordone SK, Yabsley MJ, Lund RB. Forecasting United States heartworm Dirofilaria immitis prevalence in dogs. Parasit Vectors 2016; 9:540. [PMID: 27724981 PMCID: PMC5057216 DOI: 10.1186/s13071-016-1804-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 09/19/2016] [Indexed: 11/23/2022] Open
Abstract
Background This paper forecasts next year’s canine heartworm prevalence in the United States from 16 climate, geographic and societal factors. The forecast’s construction and an assessment of its performance are described. Methods The forecast is based on a spatial-temporal conditional autoregressive model fitted to over 31 million antigen heartworm tests conducted in the 48 contiguous United States during 2011–2015. The forecast uses county-level data on 16 predictive factors, including temperature, precipitation, median household income, local forest and surface water coverage, and presence/absence of eight mosquito species. Non-static factors are extrapolated into the forthcoming year with various statistical methods. The fitted model and factor extrapolations are used to estimate next year’s regional prevalence. Results The correlation between the observed and model-estimated county-by-county heartworm prevalence for the 5-year period 2011–2015 is 0.727, demonstrating reasonable model accuracy. The correlation between 2015 observed and forecasted county-by-county heartworm prevalence is 0.940, demonstrating significant skill and showing that heartworm prevalence can be forecasted reasonably accurately. Conclusions The forecast presented herein can a priori alert veterinarians to areas expected to see higher than normal heartworm activity. The proposed methods may prove useful for forecasting other diseases.
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Affiliation(s)
- Dwight D Bowman
- College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Yan Liu
- Department of Mathematical Sciences, Clemson University, Clemson, SC, USA
| | | | - Shila K Nordone
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC, USA
| | - Michael J Yabsley
- Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine and the Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA, USA
| | - Robert B Lund
- Department of Mathematical Sciences, Clemson University, Clemson, SC, USA.
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15
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Barrantes-González AV, Jiménez-Rocha AE, Romero-Zuñiga JJ, Dolz G. Serology, molecular detection and risk factors of Ehrlichia canis infection in dogs in Costa Rica. Ticks Tick Borne Dis 2016; 7:1245-1251. [DOI: 10.1016/j.ttbdis.2016.07.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Revised: 07/05/2016] [Accepted: 07/08/2016] [Indexed: 10/21/2022]
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16
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McMahan CS, Wang D, Beall MJ, Bowman DD, Little SE, Pithua PO, Sharp JL, Stich RW, Yabsley MJ, Lund RB. Factors associated with Anaplasma spp. seroprevalence among dogs in the United States. Parasit Vectors 2016; 9:169. [PMID: 27004557 PMCID: PMC4804572 DOI: 10.1186/s13071-016-1431-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 03/05/2016] [Indexed: 11/17/2022] Open
Abstract
Background Dogs in the United States are hosts to a diverse range of ticks and tick-borne pathogens, including A. phagocytophilum, an important emerging canine and human pathogen. Previously, a Companion Animal Parasite Council (CAPC)-sponsored workshop proposed factors purported to be associated with the infection risk for tick-transmitted pathogens in dogs in the United States, including climate conditions, socioeconomic characteristics, local topography, and vector distribution. Methods Approximately four million test results from routine veterinary diagnostic tests from 2011–2013, which were collected on a county level across the contiguous United States, are statistically analyzed with the proposed factors via logistic regression and generalized estimating equations. Spatial prevalence maps of baseline Anaplasma spp. prevalence are constructed from Kriging and head-banging smoothing methods. Results All of the examined factors, with the exception of surface water coverage, were significantly associated with Anaplasma spp. prevalence. Overall, Anaplasma spp. prevalence increases with increasing precipitation and forestation coverage and decreases with increasing temperature, population density, relative humidity, and elevation. Interestingly, socioeconomic status and deer/vehicle collisions were positively and negatively correlated with canine Anaplasma seroprevalence, respectively. A spatial map of the canine Anaplasma hazard is an auxiliary product of the analysis. Anaplasma spp. prevalence is highest in New England and the Upper Midwest. Conclusions The results from the two posited statistical models (one that contains an endemic areas assumption and one that does not) are in general agreement, with the major difference being that the endemic areas model estimates a larger prevalence in Western Texas, New Mexico, and Colorado. As A. phagocytophilum is zoonotic, the results of this analysis could also help predict areas of high risk for human exposure to this pathogen. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1431-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Dongmei Wang
- Department of Mathematical Sciences, Clemson University, Clemson, SC, USA
| | | | - Dwight D Bowman
- College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Susan E Little
- Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK, USA
| | - Patrick O Pithua
- Veterinary Medical Teaching Hospital, University of Missouri, Columbia, MO, USA
| | - Julia L Sharp
- Department of Mathematical Sciences, Clemson University, Clemson, SC, USA
| | - Roger W Stich
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, USA
| | - Michael J Yabsley
- Department of Population Health, University of Georgia, Athens, GA, USA
| | - Robert B Lund
- Department of Mathematical Sciences, Clemson University, Clemson, SC, USA.
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