EFFICACY OF WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) TREATMENT FOR CATTLE FEVER TICKS IN SOUTHERN TEXAS, USA.

White-tailed deer (Odocoileus virginianus) serve as a host for cattle fever ticks (Rhipicephalus [Boophilus] microplus and Rhipicephalus [Boophilus] annulatus; CFTs); therefore, deer are a concern for CFT control programs in southern Texas, US. Systemic (oral delivery of ivermectin) and topical (permethrin on pelage) treatment devices have been developed for white-tailed deer; however, the efficacy of these treatment options has not been determined for CFTs in southern Texas. Our objectives were to evaluate the effectiveness of CFT treatment strategies by 1) measuring exposure rates of deer to the acaricides permethrin and ivermectin, 2) determining the relationship between CFTs on deer and exposure to the acaricides, and 3) determining if photos from remote cameras at medicated bait sites can be used as a measure of acaricide treatment. We captured 327 deer at four sites in southern Texas. Deer visitation to medicated bait sites was monitored using remote cameras from March 2010 to February 2012. There was no relationship between the presence of permethrin and the probability of being infested with CFTs (P≥0.336). The probability of infestation with CFTs decreased as serum ivermectin levels increased for male (n=18, P=0.098) and female (n=33, P<0.001) deer. Our results indicate ivermectin may be more effective in treating CFTs than permethrin; thus it would be worthwhile to develop topical acaricides other than permethrin for treating white-tailed deer in southern Texas.

Movement patterns of nilgai antelope in South Texas: Implications for cattle fever tick management.

Wildlife, both native and introduced, can harbor and spread diseases of importance to the livestock industry. Describing movement patterns of such wildlife is essential to formulate effective disease management strategies. Nilgai antelope (Boselaphus tragocamelus) are a free-ranging, introduced ungulate in southern Texas known to carry cattle fever ticks (CFT, Rhipicephalus (Boophilus) microplus, R. (B.) annulatus). CFT are the vector for the etiological agent of bovine babesiosis, a lethal disease causing high mortality in susceptible Bos taurus populations and severely affecting the beef cattle industry. Efforts to eradicate CFT from the United States have been successful. However, a permanent quarantine area is maintained between Texas and Mexico to check its entry from infested areas of neighboring Mexico states on wildlife and stray cattle. In recent years, there has been an increase in CFT infestations outside of the permanent quarantine area in Texas. Nilgai are of interest in understanding how CFT may be spread through the landscape. Thirty nilgai of both sexes were captured and fitted with satellite radio collars in South Texas to gain information about movement patterns, response to disturbances, and movement barriers. Median annual home range sizes were highly variable in males (4665ha, range=571-20,809) and females (1606ha, range=848-29,909). Female movement patterns appeared to be seasonal with peaks during June-August; these peaks appeared to be a function of break-ups in female social groups rather than environmental conditions. Nilgai, which reportedly are sensitive to disturbance, were more likely to relocate into new areas immediately after being captured versus four other types of helicopter activities. Nilgai did not cross 1.25m high cattle fences parallel to paved highways but did cross other fence types. Results indicate that females have a higher chance of spreading CFT through the landscape than males, but spread of CFT may be mitigated via maintenance of cattle fences running parallel with paved highways. Our results highlight the importance of documenting species-specific behavior in wildlife-livestock interfaces that can be used to develop effective disease management strategies in the United States and worldwide.

Tick-borne diseases in syntopic populations of fallow deer (Dama dama) and axis deer (Axis axis) in northern Mexico.

We harvested 21 fallow deer (Dama dama) and 17 axis deer (Axis axis) in northern Mexico. Two fallow deer were positive for Babesia bigemina and one for Babesia bovis. Amplicons had the expected 170 and 291 base pairs and were identical to B. bigemina (S45366) and B. bovis (M38218), respectively.

Serosurvey of antibodies against Toxoplasma gondii and Neospora caninum in white-tailed deer from Northern Mexico.

The objective of this study was to determine the seroprevalence of Toxoplasma gondii and Neospora caninum in white-tailed deer from Northern Mexico. Sera from 532 white-tailed deer (Odocoileus virginianus) from three Northern states of Mexico were assayed for antibodies to T. gondii by ELISA and western blot. From these samples, 368 were available to test for N. caninum antibodies by ELISA. The overall prevalence for T. gondii antibodies was 13.9% (74/532; CI(95) 11-17) and for N. caninum 8.4% (31/368; CI(95) 6-12). There was a significant association between positive ELISA results for T. gondii, with management factors within ranches, such number of deer per hectare and geographic location of deer, but none for N. caninum. T. gondii infection in the deer from Guerrero, Coahuila had an increased risk than those from Nuevo Laredo, Tamaulipas (OR, 8.3; CI(95) 1.9-35.4; P<0.05) and ranches with one deer in 15 ha had increased risk of positive association (OR, 2.61; CI(95) 1.5-4.4; P<0.05). These findings may have environmental or public health implications because venison can be an important meat source of T. gondii infections for humans and feral cats.

Epizootiology of Babesia bovis and Babesia bigemina in free-ranging white-tailed deer in northeastern Mexico.

Species of Rhipicephalus (Boophilus) ticks are the vectors of babesiosis (cattle fever tick), which are distributed worldwide. White-tailed deer (Odocoileus virginianus) are important secondary hosts for the cattle fever ticks, Rhipicephalus (B.) annulatus and Rhipicephalus (B.) microplus. White-tailed deer are capable of sustaining Boophilus spp. tick populations in the presence or absence of cattle. The objectives of this study were to determine the frequency of Babesia bovis and Babesia bigemina and the prevalence of antibodies to them and identify possible risk factors for bovine babesiosis in white-tailed deer in 3 northeastern states of México. Whole blood and serum samples (n = 457) were collected from white-tailed deer in the states of Coahuila, Nuevo Leon, and Tamaulipas during the spring of 2004. Samples were tested for B. bovis and B. bigemina by nested polymerase chain reaction (n-PCR) (the primers for B. bovis identified the gene Rap-1 and B. bigemina were specific primers) and by an indirect immunofluorescence antibody test (IFAT). A questionnaire was given to each ranch to obtain information about management practices. Logistic regression methods were used to test the association between management factors and the dependent variable of positive n-PCR or IFAT. Nineteen (4.2%) samples were positive to B. bigemina and 6 (1.7%) were positive to B. bovis by n-PCR. Serological testing showed 59.9% (n = 274) of deer sampled were positive to B. bovis and 5.4% (n = 25) were positive to B. bigemina antibodies. The logistic model varied with different dependent variables. With positive n-PCR and B. bigemina as the dependent variable, 3 factors were associated: habitat (presence of brush and exotic grasses; odds ratio (OR), 3.3; 95% confidence interval (CI), 1.3-8.5), grazing system (continuous grazing OR 4.0; CI, 1.3-12.2), and tick treatment frequency (3-4 mo; OR 7.0, CI 1.4-34.3; 5-6 mo; OR, 11.0; CI, 1.9-62.7; > 6 mo; OR, 4.6; CI, 0.9-23.3). These findings suggest that white-tailed deer may act as a reservoir for the 2 bovine Babesia spp. and that white-tailed deer may be important in the epidemiology of babesiosis. However, evidence is not available to support whether white-tailed deer are, or are not, likely to be a host that could complete the transmission cycle of Babesia spp. These results suggest that additional research is needed to demonstrate the importance of white-tailed deer as a Babesia spp. infection source for ticks.

Prevalence of infectious agents in free-ranging white-tailed deer in northeastern Mexico.

The objectives of this study were to determine the prevalence of antibodies against brucellosis, leptospirosis, infectious bovine rhinotracheitis virus, and bovine viral diarrhea virus (BVDV) in white-tailed deer (Odocoileus virginianus) in northeastern Mexico. Deer (n=521) were captured from helicopter using a netgun on 15 ranches covering 62,114 ha in the states of Coahuila, Nuevo Leon, and Tamaulipas during spring 2004. The prevalence of antibodies against Leptospira, infectious bovine rhinotracheitis, BVDV, and brucellosis were 5.6, 41.1, 63.5, and 0%, respectively, indicating that white-tailed deer and cattle may share disease agents when cohabiting in northeastern Mexico.

Immunologic and molecular identification of Babesia bovis and Babesia bigemina in free-ranging white-tailed deer in northern Mexico.

The suitability of white-tailed deer (Odocoileus virginianus) as hosts for the cattle ticks Rhipicephalus (Boophilus) microplus and Rhipicephalus (Boophilus) annulatus, has been well documented. These ticks have a wide host range, and both transmit Babesia bovis and Babesia bigemina, the agents responsible for bovine babesiosis. Although this disease and its vectors have been eradicated from the United States and some states in northern Mexico, it still is a problem in other Mexican states. It is not known if wild cervids like white-tailed deer can act as reservoirs for bovine babesiosis. The purpose of this study was to determine if B. bovis and B. bigemina or antibodies against them occur in white-tailed deer in the states of Nuevo Leon and Tamaulipas, Mexico. Twenty blood samples from white-tailed deer from two ranches were collected and tested with a nested polymerase chain reaction (nested PCR) and indirect immunofluorescence antibody test (IFAT) for B. bovis and B. bigemina. Eleven samples were positive for B. bigemina and four for B. bovis by nested PCR; amplicon sequences were identical to those reported in GenBank for B. bovis (Rap 1) and B. bigemina. Results of the IFA test showed the presence of specific antibodies in serum samples. This is the first report of the presence of B. bovis and B. bigemina in white-tailed deer using these techniques and underscores the importance of cervids as possible reservoirs for bovine babesiosis.