Despite the importance of small ruminants breeding in developing countries, milk/meat productivity remains unsatisfactory. Infectious diseases, such as leptospirosis, brucellosis, and small ruminant lentiviruses (SRLVs), contribute to this scenario. The objective of the present study was to determine the role of each of these diseases in the productivity of small ruminants breeding in Rio de Janeiro, Brazil. In goats, 343 samples were tested for leptospirosis, 560 for Brucella abortus, and 506 for caprine arthritis-encephalitis (CAE), whereas in sheep, 308 samples were tested for leptospirosis, 319 for B. abortus, 374 for Brucella ovis, and 278 for Maedi-Visna (MV). Regarding leptospirosis, 25.9% of goats and 47.4% sheep were seroreactive, with serovar Hardjo the most prevalent in both species. Anti-B. abortus agglutinins were found in 0.7% of all samples, exclusively in goats. In relation to SRLVs, 8.6% of goats and 3.2% of sheep samples were positive for CAE and MV, respectively. Leptospirosis was the major infectious problem in the small ruminants sampled and may contribute to impaired productivity of these animals.

Microsporidia are widely recognized as important human pathogens with Enterocytozoon bieneusi as the most common species infecting humans and animals, including cattle. Although Brazil has the second largest cattle herd in the world and it is the largest exporter of beef there are no data on the presence or impact of E. bieneusi on this important population. To fill this knowledge gap, fecal specimens were collected from 452 cattle from pre-weaned calves to adult cattle in the state of Rio de Janeiro. Host factors including age, gender, dairy/beef, body composition, and fecal consistency were included in the study. Using molecular methods, E. bieneusi was found in 79/452 (17.5%) fecal specimens. This represents the first report of this parasite in Brazilian cattle. A significantly higher prevalence was found in calves less than 2 months of age (27.6%) and those 3-8 months of age (28.8%) versus heifers (14.1%) and adults (1.4%) (P<0.05). Dairy cattle (26.2%) had a higher prevalence than beef cattle (9.7%) (P<0.001). No correlation was found between infection and gender, body composition, and fecal consistency. Molecular characterization of the internal transcribed spacer (ITS) revealed 12 genotypes; five previously reported in cattle (BEB4, BEB8, D, EbpA and I), and seven novel genotypes (BEB11-BEB17). A phylogenetic analysis showed that 6 genotypes (D, EbpA, BEB12, BEB13, BEB15, and BEB16) identified in 18 animals clustered within the designated zoonotic Group 1 while the other 6 genotypes (I, BEB4, BEB8, BEB11, BEB14, BEB17) identified in 61 animals clustered within Group 2. The identification of genotypes in Brazilian cattle that have previously been reported in humans highlights the potential risk of zoonotic transmission and suggests that the role of cattle in transmission of human infections requires further study.

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Toxoplasma gondii is a zoonotic agent of great importance in veterinary and public health. The aim of this study was to identify T. gondii by IHC (immunohistochemistry) in different sheep tissues and to determine if an association exists between the results obtained by this method and those obtained by the Modified Agglutination Test (MAT). Tissue specimens of twenty-six sheep seroreactive for T. gondii were selected for histopathological evaluation. The presence of T. gondii was investigated in brain, liver and heart samples by IHC and a possible anti-T. gondii antibody cross reactions with other parasites. McNemar's, Chi-square and Fisher's Exact Tests were applied for the statistical analysis of the results. The analysed tissues showed at least one of the following histopathological changes: mild-to-moderate congestion, focal polymorphonuclear inflammatory infiltrate and multifocal or focal mononuclear inflammatory infiltrate. Sarcocystis spp. were identified in the histological sections from both the heart and diaphragm tissues of 88.5% (23/26) of the animals. A total of 46.2% (12/26) of the T. gondii seroreactive sheep was also positive for T. gondii by IHC in at least one organ (brain, liver or heart). The liver IHC-positivity for T. gondii was statistically equivalent to the global individual IHC-positivity, according to McNemar's test. In addition, IHC allowed the detection of T. gondii in infected animals regardless of the titration observed in the MAT. The statistical difference observed between the three organs when comparing the low titration group, suggested that the heart might be the most suitable organ to detect T. gondii infection by IHC. The IHC results in this study revealed that almost half of MAT positive animals could serve as potential sources of infection for humans because bradyzoites were identified in different tissues, regardless of the MAT titration.

Feces were collected from 125 sheep between January and December 2007, on ten farms in the State of Rio de Janeiro, Brazil, and examined for the presence of Cryptosporidium. Ninety samples were collected from lambs 2 to 6 months of age, and 35 were from sheep over 12 months of age. All samples were subjected to molecular analysis by polymerase chain reaction (nested PCR) in two steps of the SSU rRNA. Two samples (1.6%) from the lambs were positive, and after sequencing were identified as Cryptosporidium ubiquitum. This species has been reported worldwide and it is considered a zoonotic pathogen since it has been found and in several animal species and humans. However, because of the low frequency of C. ubiquitum found, the risk for public health in this region may not be high.

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Toxoplasma gondii is one of the most widely studied parasites due to its medical and veterinary importance. The parasitic infection of sheep occurs worldwide, with studies showing prevalences ranging from 1.8% in North Tunisian to 95.7% in Turkey. In this ruminant species, infection with T. gondii causes fetal death, mummification, stillbirth, the birth of debilitated animals and frequent abortion. The latter has been reported as the primary cause of economic losses in the sheep industry because of the high rates of infection. Concerns over toxoplasmosis infections in sheep, as well as the economic losses they can cause, induced this literature review. A review of the topic will provide the reader with some basic information concerning the importance of this parasite in the sheep industry in Brazil and worldwide, which might assist in controlling the disease and promptly identifying the problem in a flock, thus avoiding losses from potential abortions caused by this important parasite.