Prevalence and risk factors of Neospora caninum and Toxoplasma gondii infection in breeding ewes from central western Mexico.

The objective of the study was to analyse the prevalence of infection by N. caninum and T. gondii in breeding ewes from central western Mexico. For this purpose, 184 blood samples were collected from sheep in the reproductive stage, which were analysed by ELISA and PCR tests, respectively, and the association between seroprevalence and some management factors was estimated by means of a logistic regression analysis. For N. caninum, a seroprevalence of 15.22% was identified, while the DNA detection in blood was 14.13% (26/184); positive animals were found in 75% of the farms (6/8). The variables poor placental waste management (OR 8.4), abortion history (OR 1.5) and presence of rodents (OR 1.3) were identified as risk factors for N. caninum infection. In the case of T. gondii, a seroprevalence of 61.96% was found, and antibodies were detected in eight farms included in the study; no positive samples were identified for T. gondii by the PCR test. The main identified risk factors for T. gondii were as follows: poor hygiene conditions (OR 12.5), presence of cats (OR 9.5), presence of other domestic animals (OR 5.7), urban context of the farm (OR 9.5) and public water supply (OR 5.3). The seroprevalence of co-infection of T. gondii and N. caninum in breeding ewes was 7% (13/184; 95% CI 6.92-7.20). T. gondii has a high seroprevalence while N. caninum was of lower proportion, and both may be associated with reproductive losses for these herds studied.

Seroprevalence of Toxoplasma gondii Infection and Associated Factors in Sheep from Jalisco, Mexico.

The objective of the study was to identify the seroprevalence of anti-Toxoplasma gondii antibodies in sheep herds from 3 municipalities from Jalisco, Mexico, as well as estimate the association between seroprevalence and certain factors presents in the farms. In total, 12 sheep farms that maintain only hair breeds were included in the work. From these farms, 336 blood samples were collected, corresponding 324 to ewes and 12 rams. Serum samples were subjected to ELISA test, and the association between the frequency of antibodies and some potential risk factors was estimated. The overall seroprevalence to anti-T. gondii antibodies in the population studied was 17.8% (60/336; 95% confidence interval [C.I.] 14-22), all farms had positive animals, and the seroprevalence of antibodies ranged between 7 to 32%. Seroprevalence in specific municipalities was 18.7% in Lagos de Moreno, 17.8% in Encarnación de Díaz, and 16.9% in San Juan de los Lagos. Seroprevalence in ewes was 17.5% (57/324; 95% C.I. 13-22), and seroprevalence in rams was 25% (3/12; 95% C.I. 6-57), while among breeds it was 17.8% in Pelibuey (20/112; 95% C.I. 11-26), 16.6% in Kathadin (14/84; 95% C.I. 9-26), 15.4% in Blackbelly (13/84; 95% C.I. 8-25), and 23.2% in Dorper (13/56; 95% C.I. 13-36); no differences were observed among breeds (p < 0.05). The presence of cats on the farms was associated with seroprevalence (odds ratio [OR] 2.8; 95% C.I. 1.8-7.3, p < 0.001), as was the absence of a rodent-control program (OR 1.5; 95% C.I. 0.8-3.2, p < 0.05). No other factors were identified as associated with seroprevalence.

Prevalence, Incidence, and Risk Factors for Infection by Neospora caninum in Dairy Farm Dogs in North-Central Mexico.

The purpose of this study was to describe the prevalence and incidence of Neospora caninum infection in dogs that are in close contact with dairy cattle and to identify possible risk factors associated with the infection in this population. Twenty-four dogs located in 8 different dairy farms of Aguascalientes, Mexico, were evaluated for a 6-mo period. Once a month a sample of serum and a sample of peripheral blood was collected. The serum was used to detect antibodies against N. caninum by means of the indirect immunofluorescence technique, and the blood was used to detect parasite's DNA. The association between seroprevalence and possible risk factors was estimated using logistic regression. The prevalence of anti-N. caninum antibodies was 54% in the first month, 62% in the last month, and the incidence was 8.69%. One farm had no positive cases. Antibody titers ranged from 1:50 to 1:800. Parasite DNA was not detected in any of the samples. Only the age (>6 yr) of the dogs was identified as a risk factor for infection by N. caninum (P ≤ 0.05).

Short communication: Relationship between serum cortisol concentration and defensive behavioral responses of dairy cows exposed to natural infestation by stable fly, Stomoxys calcitrans.

The aim of this study was conducted to evaluate the effect of natural infestation by Stomoxys calcitrans on the behavioral and adrenocortical responses of dairy cattle. Twenty Holstein cows randomly selected were individually sprayed with insecticide once every 7d, whereas no insecticide was applied to the other 20 animals. The average number of flies per cow was estimated daily, and the frequency of fly-avoidance behaviors was measured daily; plasma cortisol concentration was measured each morning. No flies were ever counted on the treated cows at any time during the experiment, whereas an average of 17.13±1.14 (±standard error) flies/d were recorded on untreated cows. Tail movement was the most frequent behavior displayed, with stamps or kicks showing the highest increment rate (41.2×) when fly population increased from zero to greater than 51 flies/cow. Cortisol concentration increased to a maximum of 56.81±39.53ng/mL with 26 to 30 flies/cow per day. Coefficients of determination between the number of flies, cortisol concentration, tail movements, and stamps or kicks were 0.73, 0.78, and 0.81, respectively. The multiple correlation coefficient was 0.90, with 81% of the variation in cortisol concentration explainable by variation in the number of flies per cow and the frequency of fly-avoidance behaviors. It was concluded that plasma cortisol concentration is linearly related to a combination of the number of flies and the frequency of fly-dislodging behaviors, producing a maximum response before reaching maximum fly loads.

Efficacy of the entomopathogenic fungi Metarhizium anisopliae in the control of infestation by stable flies Stomoxys calcitrans (L.), under natural infestation conditions.

The objective of this study was to evaluate the efficacy of an isolate of Metarhizium anisopliae applied by aspersion to control of Stomoxys calcitrans flies in dairy cattle naturally infested. Was applied by aspersion an aqueous formulation of M. anisopliae sensu lato (Ma134), at a concentration of 1×10(8)conidia/ml, four times with seven day intervals, on a group of eight Holstein cows; a control group of eight Holstein cows, received a water solution with Tween 80 (0.1%). The average number of flies per animal was estimated one day before each application, and then daily counts were done in both groups. The effectiveness of the formulation was calculated using the Abbott's formula. At the same time, defensive behaviors of stamp/kicks and tail movements were evaluated daily, estimating relative frequency per hour. The Ma134 formulation had an infestation control efficacy of 73%, taking into consideration the four study weeks. The population reduction effect was observed since the first week post-application (p<0.05), and the effect increased with the subsequent applications. Defensive behaviors were reduced beginning from the first application, reaching a reduction of 66% and 70%, respectively, during the four weeks of study. These results demonstrated the effectiveness of the formulation to control infestation by S. calcitrans, as well as reduce defensive behaviors which involves the infestation.

Relationships between stable fly infestation with some physical facility characteristics and sanitation practices in several dairy farms in the State of Aguascalientes, Mexico.

The possible relationships between stable fly infestation with dairy farm facilities and sanitation practices were studied using path analysis. Twelve dairies located in four counties of Aguascalientes dairy region were selected. The dairies were monitored from May to November 2003. In each occasion, fly infestation, individual physical facility characteristics, and sanitation practices were recorded. In all, 11 independent variables were involved in the study and related variables were grouped together and analyzed in two blocks by path analysis for each one of five population events (begin of fly season, first peak, fluctuation, second peak and decrease). There were significant regression coefficients only in the second peak for two variables, the distance to the silos and the distance to the dung heap (r(2)=0.96 for the full model). Among the 11 variables examined in the study, none had a statistical significant indirect contribution to fly infestation; direct contribution was observed for distance to the silos and for distance to the dung heap variables. However, only the distance to the silos variable was significantly related to stable fly Infestation.