The levels of infection by Babesia bovis and Babesia bigemina were estimated by absolute quantification through the quantitative PCR technique (qPCR). Fifty-one contemporaneous Angus cattle were evaluated on two occasions. The number of standard female Rhipicephalus microplus ticks present on the left side of the body was counted and blood samples were drawn from the tail vein into tubes containing the anticoagulant EDTA. The blood samples were submitted to DNA extraction and used to quantify the number of copies (NC) of DNA from B. bovis and B. bigemina by qPCR. The data on tick count and number of DNA copies were transformed for normalization and analyzed by a mixed model method. A multivariate model with repeated measures of the same animal, including the effects of collection, parasite species and their interaction, was used. The repeatability values were obtained from the matrix of (co)variances and were expressed for each species. The correlations between the counts of different species on the same animal, in the same collection or different collections, were also estimated. The results showed the qPCR could distinguish the two between infection by the two Babesia species. Infection levels by B. bovis and B. bigemina were detected in 100% and 98% of the animals, respectively. Significant differences were found (P<0.05) between the NC of the two Babesia species, B. bovis 1.49±0.07 vs. B. bigemina 0.82±0.06. Low repeatabilities were found for the counts of R. microplus and NC of B. bovis and B. bigemina: 0.05, 0.10 and 0.02, respectively. The correlations between R. microplus count and NC of B. bovis and B. bigemina were both very near zero. However, an association was observed between the NC of the two species, with a correlation coefficient of 0.30 for measures from the same collection. The absence of associations between the quantity of DNA from B. bovis and B. bigemina and the tick counts suggests that the variation of parasitemia by the hemoparasites did not depend on the tick infestation levels at the moment of each collection. The repeatability values estimated indicate that under the study conditions, the variations in the tick infestation levels and of parasitemia by B. bovis and B. bigemina depend more on factors related to each collection than on intrinsic factors of the animal.

No abstract

Rhipicephalus microplus is a vector of cattle tick fever, a disease caused by the protozoans Babesia bovisand B. bigemina, and also anaplasmosis, produced by the Rickettsiales Anaplasma marginale. These tick-borne pathogens cause considerable losses to Brazilian livestock breeders and represent an obstacle to the expanded use of taurine breeds due to their higher sensitivity to ticks and hemoparasites compared to zebu breeds. Differences in the susceptibility to hemoparasites were also verified within breeds, suggesting that may be possible to select a most resistant phenotype. Therefore, repeatability of R. microplus counts and copy number of hemoparasites DNA were estimated, along with correlations between themselves, aiming to verify if those measures can be used as parameters to classify animals according to their parasite resistance degrees. Forty-two Canchim females kept on pastures naturally infested by ticks were evaluated for the level of infestation by R. microplus and infection by B. bovis, B. bigemina, and A. marginale. Twenty-four evaluations were performed once a month, for adult female ticks counts and blood samplings. The experimental period was divided into four phases, according to the animals age range: Phase 1: 8 to 13 months (collections 1 to 6); phase 2: 14 to 19 months (collections 7 to 12); phase 3: 20 to 25 months (collections 13 to 18), and phase 4: 26 to 31 months (collections 19 to 24). Blood samples were submitted to absolute quantification of hemoparasites DNA sequences using qPCR. The hemoparasite and tick counts data were transformed for normalization and were analyzed using mixed models. Among three species of hemoparasites studied, A. marginale presented the highest level of infection. During phase 3, B. bigemina presented higher infection levels (p < 0.05) compared to B. bovis, whereas no differences were observed in other phases. Estimated repeatabilities for parasite infection levels varied from low to moderate during our experiment. There were low correlations between tick counts and parasite infection levels, and between parasite infection levels from different species by themselves. Based on these results, under conditions of the present study, we suggest that it is possible to identify animals presenting a most resistant phenotype against infection by both hemoparasites and ticks. Moreover, the animal age may be an important factor related to resistance against these pathogens. The data obtained shed more light on the resistance to hemoparasites studied.

With the aim of finding quantitative phenotypic traits that can be used to discriminate the levels of resistance/susceptibility to Babesia bovis, we estimated the repeatability and correlation between the level of infection, determined by the number of copies of a fragment of the gene that encodes cytochrome B (NC mt-cyB) of B. bovis, and the levels of the anti-B. bovis antibodies, in blood samples collected from 51 Angus cattle on two different occasions. Samples with the anticoagulant EDTA were used for DNA extraction and without anticoagulant for separation of the blood serum. The quantification of the NC mt-cyB of B. bovis was carried out by the quantitative PCR technique (qPCR), while the anti-B. bovis IgG antibody titers (S/P) were quantified by the ELISA method. The NC and S/P data were log10-transformed to improve the approximation to the normal distribution and were analyzed using mixed models. The correlations between NC mt-cyB and S/P were estimated, as well as the repeatability values for each trait. The results obtained showed the high sensitivity of the techniques, with 100% of the animals being positive for B. bovis, detected by both the serological and molecular tests. The correlations estimated between NC and S/P were low, 0.10 and 0.12, in the first and second collection, respectively. The repeatability estimated for NC was 0.06, whereas for the S/P it was 0.42. The low correlations between S/P and NC in the two collections demonstrated that the variation in the NC value is independent of the level of antibodies. This results indicated that animals with a higher levels of antibodies against B. bovis in the first collection continued to have a higher levels in the second one. However, the very low values for the repeatability value of NC, and for the correlations between S/P and NC, demonstrates that neither NC or S/P could be used to discriminate animals for resistance/susceptibility to B. bovis.

No abstract

The use of silvopastoral systems (SPS) can be a good alternative to reduce the environmental impacts of livestock breeding in Brazil. Despite the advantages offered by public policies, many producers hesitate to use this system. One of the reasons is the lack of information on health and productivity of cattle raised under these conditions. The experiment reported here was designed to compare the behavior of infection by gastrointestinal nematodes and weight gain of beef cattle raised in a SPS and a conventional pasture system. We monitored the number of eggs per gram of feces, the prevalent nematode genus, data on climate, forage availability, weight gain and packed cell volume (PCV) of the animals bred in the two systems. The infection by nematodes was significantly higher in the cattle raised in the SPS (p \ 0.05). The coprocultures revealed the presence of nematodes of the genera Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus, in both systems, but the mean infestation rates of Haemonchus and Cooperia were higher in the SPS (p \ 0.05). The average of PCV values did not differ between the cattle in the two systems. The individual weight gain and stocking rate in the period did not vary between the systems (p [ 0.05). Despite the higher prevalence of nematodes in the SPS, no negative impact was detected on the animals' weight gain and health. The results of this experiment indicate that under the conditions studied, there is no need to alter the parasite management to assure good productive performance of cattle.

The use of silvopastoral systems (SPS) can be a good alternative to reduce the environmental impacts of livestock breeding in Brazil. One of the reasons for its scarce adoption is the lack of information on health and productivity of cattle raised under these conditions. The experiment reported here was designed to compare the infestation by external parasites - the cattle tick (Rhipicephalus microplus), horn fly (Haematobia irritans), and larvae of the botfly (Dermatobia hominis) - in beef cattle raised in a SPS and a conventional pasture system (CPS), evaluated for 24 months. Data on air and soil temperature, solar radiation, wind incidence and water balance were used to characterize the SPS and CPS. R. microplus adult females and D. hominis larvae were counted on the body of each animal to determine the parasites burdens, but we did not find significant differences between the two systems. Horn flies counts on animals' body, and analysis of the horn fly and its pupal parasitoids associated with the dung pats were obtained in the two systems. Horn fly infestation was significantly lower (p=0.01) in the SPS (13.17±3.46) in comparison with the CPS (24.02±4.43). In SPS and CPS, respectively, the mean densities of pupae of H. irritansin dung pats were 9.8 and 10.7; the mean density of adults of H. irritans, 3.7 and 3.5; and the density of its pupal parasitoids were 20.5 and 5.4. The effect of production system was significant (p<0.05) only for the occurrence of pupal parasitoids of the horn fly, where the greatest occurrences of these natural enemies were in the SPS. These data indicate that natural enemies were able to control, at least partially, the horn fly populations in the cattle.

Babesiosis is a tick-transmitted disease that causes severe economic losses to the cattle industry in Brazil. Water buffaloes (Bubalus bubalis) are often carriers of Babesia spp., but there are no studies that provide an accurate estimation of this infection in animals raised in regions of endemic stability. This study was conducted to investigate Babesia bovis and B. bigemina infections in 108 water buffaloes (50 calves and 58 adult females) located in areas of São Paulo state, where the animals were continuously exposed to Rhipicephalus microplus ticks. B. bovis and B. bigemina infections were screened by microscopic examination of blood smears, nested PCR (nPCR) and quantitative real-time PCR (qPCR), which were also used to estimate the number of copies (NC) of the cytochrome b (mt-cytB) gene in the blood samples. B. bigemina was found in blood smears of three calves from Alambari herd (all with less than 0.1% parasitemia). Molecular techniques were more sensitive than blood smears to diagnose piroplasms in water buffaloes: 20.37% and 100.00% for B. bovis-infected animals and 59.26% and 100.00% for B. bigemina-infected animals, respectively for nPCR and qPCR. The NC of mt-cytB gene of B. bovis and B. bigemina in blood samples re-* Corresponding author. T. A. Néo et al. 76 vealed significant effects (p < 0.05) of herd-age, species and their interaction. The NC values were higher (p ≤ 0.05) for B. bigemina (2.80 ± 0.06) than for B. bovis (2.61 ± 0.05). Within each herd-age, differences between the species' NC values were found only in Alambari calves, which showed significantly higher (p ≤ 0.05) NC of B. bigemina (3.48 ± 0.13). The calves and cows from Ibaté showed the lowest NC of B. bigemina (2.29 ± 0.13 and 2.63 ± 0.14) and B. bovis (2.54 ± 0.11 and 2.37 ± 0.12), respectively. These data suggest a high prevalence of B. bovis and B. bigemina infection in the buffalo population in endemic areas of São Paulo state.