Evaluating the utility of companion animal tick surveillance practices for monitoring spread and occurrence of human Lyme disease in West Virginia, 2014-2016

Domestic dogs and cats are potentially effective sentinel populations for monitoring occurrence and spread of Lyme disease. Few studies have evaluated the public health utility of sentinel programmes using geo-analytic approaches. Confirmed Lyme disease cases diagnosed by physicians and ticks submitted by veterinarians to the West Virginia State Health Department were obtained for 2014-2016. Ticks were identified to species, and only Ixodes scapularis were incorporated in the analysis. Separate ordinary least squares (OLS) and spatial lag regression models were conducted to estimate the association between average numbers of Ix. scapularis collected on pets and human Lyme disease incidence. Regression residuals were visualised using Local Moran’s I as a diagnostic tool to identify spatial dependence. Statistically significant associations were identified between average numbers of Ix. scapularis collected from dogs and human Lyme disease in the OLS (β=20.7, P\u3c0.001) and spatial lag (β=12.0, P=0.002) regression. No significant associations were identified for cats in either regression model. Statistically significant (P≤0.05) spatial dependence was identified in all regression models. Local Moran’s I maps produced for spatial lag regression residuals indicated a decrease in model over- and under-estimation, but identified a higher number of statistically significant outliers than OLS regression. Results support previous conclusions that dogs are effective sentinel populations for monitoring risk of human exposure to Lyme disease. Findings reinforce the utility of spatial analysis of surveillance data, and highlight West Virginia’s unique position within the eastern United States in regards to Lyme disease occurrence

Incidence of and risks associated with Giardia infections in herds on dairy farms in the New York City Watershed

<p>Abstract</p> <p>Background</p> <p>The primary aims of this study were to determine the incidence of <it>Giardia </it>infections in dairy herds on farms in the New York City Watershed region and to evaluate risk factors associated with infections. Because co-infections of <it>Giardia </it>and <it>Cryptosporidium </it>spp. are common in this population, we also evaluated the effect of herd infection status on <it>Giardia </it>infections.</p> <p>Methods</p> <p>Farms were grouped into three cohorts based on their prior infection status with <it>Giardia </it>and/or <it>Cryptosporidium </it>spp. The sampling plan included collecting fecal samples from all calves below 30 days of age and proportional sampling of calves, young stock, and adults. A total of 10,672 fecal samples were collected and analyzed for the presence of <it>Giardia </it>cysts using zinc sulfate flotation. Herds enrolled in the study were sampled seasonally for a study period of two years. The probability of shedding cysts past a certain age and the factors that influenced the likelihood of shedding were evaluated using survival analysis. Linear regression was used to evaluate factors that were associated with the intensity of shedding.</p> <p>Results</p> <p>The majority of <it>Giardia </it>infections occurred in calves within their first 180 days of age, with the most number of calves shedding <it>Giardia </it>cysts between 11 and 20 days of age. The incidence of shedding of <it>Giardia </it>cysts ranged from 0.0004 per animal day for cattle in the low risk cohort to 0.0011 per animal day for cattle in the high risk cohort. The likelihood of shedding was influenced by the prior infection status of the herd and the season of collection. Infected animals shed on average 9,658 cysts/gram and the intensity of shedding <it>Giardia </it>cysts varied significantly with the age (p < 0.0001) and the season of collection (p = 0.0151 for Spring).</p> <p>Conclusion</p> <p><it>Giardia </it>infections are common in dairy herds in the New York City watershed, particularly in calves less than 6 months of age. Seasonality may be an important factor in the perpetuation of infections based on changes in management practices corresponding to weather patterns of a particular season. A dairy herd's prior infection status with <it>Cryptosporidium </it>influences the likelihood of infection with <it>Giardia</it>.</p

Potential Zoonotic Risk Of Giardia Duodenalis Infections From Livestock And Companion Animals

Transmission of Giardia duodenalis infections from animals to humans has been a subject of recent research interest. Several reports have shown animals harboring strains of G. duodenalis that have also been identified from human samples. Much of the work assessing the organism's zoonotic potential has been done on livestock and companion animals, given high prevalence rates, high intensity of shedding, and their relationships with humans as domesticated species. The research presented in this dissertation is a compilation of four complementary studies aimed at assessing the zoonotic potential of Giardia duodenalis infections in dairy cattle and dogs. The first study was a longitudinal cohort study in which the incidence of Giardia infections was evaluated in dairy cattle in the New York City Watershed encompassing Delaware, Greene, Schoharie, Ulster, and Sullivan counties in New York. Three cohorts were analyzed based on their prior infection status with Giardia. 10,672 fecal samples were collected from calves and adult cattle from 40 dairy herds. The cumulative incidence was 25% over the course of the two-year study. Risk factors such as age, prior infection status, and season of sampling were shown to be significantly associated with shedding Giardia cysts. The second study was a repeated prevalence study done on the same target population described in the first study. The major goal was to determine the prevalence of assemblages of G. duodenalis in dairy cattle in order to genetically characterize infections. 2,109 samples were collected of which 504 were positive for Giardia based on fecal flotation for a cumulative incidence of 23.9%. Polymerase chain reaction (PCR) of the beta-giardin and triosephosphate isomerase genes with subsequent DNA sequencing revealed livestock-specific and potentially zoonotic genotypes in dairy cattle in the New York City Watershed. The third study was a cross-sectional study with aims to 1) determine the prevalence of G. duodenalis in dairy cattle in Trinidad and Tobago, 2) conduct multi-locus characterization of G. duodenalis infections using PCR, and 3) identify risk factors associated with G. duodenalis infections in this population. One hundred and ninety-six samples were analyzed by PCR of the small-subunit ribosomal RNA (ssu-rRNA) gene as the only diagnostic test. Twenty-five samples were positive for a prevalence of 12.8%. Of the ssu-rRNA positive samples, ten were positive by PCR amplification of the beta-giardin gene. Three samples showed heterogeneity of assemblage typing between the two loci, likely indicating mixed infections of assemblages A and E. The final study was a cross-sectional study done on owned, shelter, and free-roaming dogs in Trinidad and Tobago. The major goals were to 1) determine the prevalence of G. duodenalis infections in dogs, 2) assess the risk of G. duodenalis infections to humans through genetic characterization of isolates, 3) compare test agreement between a commercially-available ELISA test kit for Giardia and PCR, and 4) identify risk factors associated with G. duodenalis infections in dogs. 104 samples were analyzed by PCR of the ssu-rRNA gene of which 26 were positive for a prevalence of 25%. No zoonotic strains were present in the study population. Dogspecific assemblages C and D were found as well as one sample identified as assemblage E. The kappa statistic for agreement between PCR and ELISA was 0.67 indicating good agreement between the tests. Risk factors for infection in dogs included age, group housing, and ownership status. These findings contribute to greater understanding of the zoonotic potential of G. duodenalis infections in dairy cattle and dogs. The New York Watershed studies highlight growing public health concerns about zoonotic pathogens in the public water supply. The work done in Trinidad and Tobago represents pilot epidemiologic research on G. duodenalis infections from livestock and companion animals and contributes to our knowledge about the global distribution of G. duodenalis. While these studies do not directly link infections in dairy cattle and dogs to humans, they provide information on risk factors that may perpetuate G. duodenalis infections in these populations, other animal populations and humans. Taking significant risk factors into consideration may reduce the occurrence of G. duodenalis infections in dairy cattle and dogs, thereby indirectly reducing the potential for infections in humans

Evaluating the utility of companion animal tick surveillance practices for monitoring spread and occurrence of human Lyme disease in West Virginia, 2014-2016

Domestic dogs and cats are potentially effective sentinel populations for monitoring occurrence and spread of Lyme disease. Few studies have evaluated the public health utility of sentinel programmes using geo-analytic approaches. Confirmed Lyme disease cases diagnosed by physicians and ticks submitted by veterinarians to the West Virginia State Health Department were obtained for 2014-2016. Ticks were identified to species, and only Ixodes scapularis were incorporated in the analysis. Separate ordinary least squares (OLS) and spatial lag regression models were conducted to estimate the association between average numbers of Ix. scapularis collected on pets and human Lyme disease incidence. Regression residuals were visualised using Local Moran’s I as a diagnostic tool to identify spatial dependence. Statistically significant associations were identified between average numbers of Ix. scapularis collected from dogs and human Lyme disease in the OLS (β=20.7, P<0.001) and spatial lag (β=12.0, P=0.002) regression. No significant associations were identified for cats in either regression model. Statistically significant (P≤0.05) spatial dependence was identified in all regression models. Local Moran’s I maps produced for spatial lag regression residuals indicated a decrease in model over- and under-estimation, but identified a higher number of statistically significant outliers than OLS regression. Results support previous conclusions that dogs are effective sentinel populations for monitoring risk of human exposure to Lyme disease. Findings reinforce the utility of spatial analysis of surveillance data, and highlight West Virginia’s unique position within the eastern United States in regards to Lyme disease occurrence