Techniques for monitoring dairy calves against the tick fever agents: a comparative analysis.

Data regarding parasitemia (blood smears), rectal temperature (RT), packed cell volume (PCV) and vaginal mucosa coloration (VMC) of Gyr x Holstein female calves between 3-7mo were accessed to evaluate different techniques for monitoring the bovine tick fever agents (TFA). The 1st experiment determined the correlation between the TFA parasitemia with RT and PCV. The 2nd, evaluated the associated risk of A. marginale parasitemia with RT and PCV in relation to the Gyr/Holstein genetic proportion (5/8,3/4,7/8 and 15/16) using Receiver Operating Characteristic Curve (ROC). The 3rd, two groups were performed: cattle monitored by RT (T01) and by PCV (T02), during their 80-210 days of age, data regarding TFA parasitemia, RT, PCV, VMC and weight were registered. In 1st experiment, RT showed weak correlation with TFA parasitemia, while PCV showed a strong correlation with A. marginale and B. bigemina, but not with B. bovis parasitemia. In experiment 2, the ROC curve analysis showed that when the genetic proportion of B. t. taurus increased, least reliable RT was to monitor calves infected with A. marginale. The PCV for monitoring A. marginale was the best technique, showing sensitivity of 74.2% and specificity of 97.0% than other techniques that used RT and VCM as a monitoring tool. In general, calves monitored by PCV (T02) showed higher PCV values, lower A. marginale parasitemia, less pneumonia as co-infection and less salvation treatment were performed than in animals monitored by RT (T01). Furthermore, animals from T02 gained 23.5 kg more than those from T01. The low frequency of B. bovis and B. bigemina found in this study made impossible to compare the monitoring techniques for these pathogenic agents.

Eimeria spp. in naturally infected beef cattle: Dynamics of oocysts excretion, prevalence, and comparison between parasitological diagnostics.

Eimeria spp. infections cause mortality, reduced well-being, and substantial economic losses implications for cattle production worldwide. The present work followed up the excretion of Eimeria spp. oocysts in two naturally infected beef herds, from two different properties, to investigate the dynamics of oocyst excretion and the prevalence of Eimeria spp. in different animal categories and seasons of the year (rainy season - October to April; dry season - May to September). Even that, the species of Eimeria were identified and the parasitological techniques of Gordon and Whitlock modified and Mini-FLOTAC were used. In both herds, animals up to 14 months had a mean total OPG counts higher than older animals (after 15-16 months of age), and the species E. zuernii and E. bovis were more frequently identified, the first species being more frequent in animals from 1 to 2 months of age, while E. bovis prevailed from three months old. On property 1, the highest mean OPG counts (P ≤ 0.05) were obtained between October 2017 and September 2018, with the highest mean OPG counts in October 2017, when the animals were aged between 4-5 months. The prevalence of the pathogen on property 1 was 59.16 % and 43.62 % in the rainy and dry season, respectively, a higher parasitic load (P ≤ 0.05) was verified in the rainy season. On property 2, the mean OPG counts of Eimeria spp. was higher (P ≤ 0.05) in animals between 8-16 months, with the highest peak in November 2019, when they were one year old. The on-site prevalence during the rainy season on property 2 was 53.09 % and 49.79 % on dry season, and no difference (P = 0.92) in the mean OPG counts of Eimeria spp. during the seasons. There was a difference (P ≤ 0.05) in the count of oocysts in females after 18 months of age than males, which was probably due to the increase in animal density. Both tested techniques can be used for quantification of the excretion of oocysts of Eimeria spp. in cattle feces showing the same OPG mean count (r = 0.9287; p = 0.0025; R² = 0.8625). Mini-FLOTAC showed higher prevalence for Eimeria spp., however, can be an obstacle depending on the number of fecal samples that need to be processed.