[show abstract][hide abstract] ABSTRACT: Climate and environmental data were used to estimate the risk of testing positive for antibodies to bluetongue (BTV) and epizootic hemorrhagic disease viruses (EHDV) in cattle in Illinois and western Indiana over three transmission seasons (2000-2002). The risks of BTV and EHDV seropositivity were positively associated with temperature during every year of the study. The EHDV seropositivity was also positively associated with forest patchiness in two of the years. During 2002, a year with unusually high spring rainfall, forest patchiness was not significantly associated with EHDV but spring rainfall did have a moderating effect on temperature. Maps of predicted probability of exposure to BTV or EHDV were created using these best-fitting models and show distinctly different spatial patterns within the same cattle population.
The American journal of tropical medicine and hygiene 10/2010; 83(4):789-94. · 2.53 Impact Factor
[show abstract][hide abstract] ABSTRACT: To estimate seroprevalence of antibodies against the serogroup of epizootic hemorrhagic disease viruses (EHDVs) and describe spatial distribution of antibodies against EHDV among cattle herds in Illinois and western Indiana.
9,414 serum samples collected from cattle in 60 herds over 3 transmission seasons.
Serum samples were tested for antibodies against EHDV by use of an ELISA. Seroprevalence for 4 zones covering the length of Illinois and parts of Indiana were estimated. A multivariable mixed-effects logistic regression model with a random effect for herd was used to estimate seropositive risk for zone (1 through 4), age (yearling, adult), herd type (beef, dairy), transmission season (2000 to 2002), and zone by year interaction. Isopleth maps of seroprevalence at the herd level were produced.
Antibodies against EHDV were detected in 1,110 (11.8%) samples. Estimated seroprevalence in 2000, 2001, and 2002 was 15.3%, 13.4%, and 5.2%, respectively. Seroprevalence was highest in the southernmost zone and lowest in the northernmost zone, but risk of seropositivity for EHDV among and within zones varied by year. Clusters of high seroprevalence in the south, low seroprevalence in the north, and outliers of high and low seroprevalence were detected. Risk mapping revealed areas of higher seroprevalence extending northward along the western and eastern ends of the study region.
Seroprevalence of antibodies against EHDV in cattle was higher in the south than north; however, local complexities existed that were not observed in a serosurvey of antibodies against bluetongue virus from the same cattle population.
American Journal of Veterinary Research 11/2008; 69(10):1286-93. · 1.35 Impact Factor
[show abstract][hide abstract] ABSTRACT: To estimate seroprevalence of bluetongue virus (BTV) and the geographic distribution of seropositive cattle herds in Illinois and western Indiana.
10,585 serum samples obtained from cattle in 60 herds during 3 transmission seasons (2000 through 2002).
In a longitudinal study, serum samples were tested for BTV antibodies by use of a competitive ELISA. Four geographic zones were created by use of mean minimum January temperature. A multivariable mixed-effects logistic regression model with a random effect for herd was used to estimate seropositive risk for zone, age of cattle, herd type, and transmission season.
Overall, BTV antibodies were detected in 156 (1.5%) samples. Estimated seroprevalence in 2000, 2001, and 2002 was 1.49%, 0.97%, and 2.18%, respectively. Risk of being seropositive for BTV was associated with geographic zone and age. Seroprevalence increased progressively from northern to southern zones, with no evidence of BTV infection in the northernmost zone. In the southernmost zone, annual seroprevalence ranged from 8.65% to 11.00%. Adult cattle were 2.35 times as likely as juvenile cattle to be seropositive.
Overall seroprevalence was lower than has been reported for Illinois cattle. Bluetongue virus antibodies were distributed heterogeneously in this region. Only in the southernmost zone was seroprevalence consistently > 2%. Regionalization of BTV risk based on state borders does not account for such variability. Serologic data could be combined with landscape, climate, and vector data to develop predictive models of BTV risk within transitional regions of the United States.
American Journal of Veterinary Research 11/2007; 68(11):1212-9. · 1.35 Impact Factor
[show abstract][hide abstract] ABSTRACT: Bacterial resistance to antibiotics continues to pose a serious threat to human and animal health. Given the considerable spatial and temporal heterogeneity in the distribution of resistance and the factors that affect its evolution, dissemination and persistence, we argue that antibiotic resistance must be viewed as an ecological problem. A fundamental difficulty in assessing the causal relationship between antibiotic use and resistance is the confounding influence of geography: the co-localization of resistant bacterial species with antibiotic use does not necessarily imply causation and could represent the presence of environmental conditions and factors that have independently contributed to the occurrence of resistance. Here, we show how landscape ecology, which links the biotic and abiotic factors of an ecosystem, might help to untangle the complexity of antibiotic resistance and improve the interpretation of ecological studies.