Survey for the presence of Neospora caninum in frozen bull's semen samples by PCR assay

Investigation of Tritrichomonas foetus in cryopreserved bovine semen by culture and polymerase chain reaction

ABSTRACT Bovine Trichomoniasis (BT) is an infectious disease caused by Tritrichomonas foetus that can be transmitted either sexually or by fomites. In males, the disease is asymptomatic and permanent. T. foetus has been detected in semen samples where it is able to remain viable even when frozen. The objective of this study was to investigate the presence of T. foetus in 27 samples of commercial frozen bovine semen by culture and Polymerase Chain Reaction (PCR). Samples were thawed in water at 37°C. Part of the samples was inoculated in a test tube containing Diamond’s medium and incubated at 35°C. Growth was evaluated every 24 hours via direct examination under a microscope. The other part was placed in an Eppendorf tube and frozen for later molecular analysis. After 10 days of culture, all samples were negative for T. foetus. The Quick-DNA Miniprep Kit (Zymo Research) without proteinase K was used for DNA extraction. The primers used in PCR were TRF3 and TRF4. PCR results were negative for all samples. In conclusion, bovine semen samples were negative for T. foetus in both diagnostic methods, according to the adopted methodology.

Neosporosis in bulls: potential for venereal transmission, and effect on semen quality and production

Neospora caninum caninum is a protozoan parasite that can cause abortions, birth of congenitally infected calves, and reduced milk production in cattle. Neosporosis in cattle can be transmitted through vertical transplacental transmission from dam to calf, or through horizontal transmission between animals. While it is well established that horizontal transmission from dogs (the definitive host) to cattle (an intermediate host) occurs, it is not clear whether horizontal transmission may occur between cows and bulls during mating. Transmission via infected semen of seropositive bulls was suggested when N. caninum DNA was found in bull semen. The primary objective of this article is to critically evaluate the evidence for venereal transmission of N. caninum between cattle, to determine whether this transmission route is likely to occur. A secondary objective is to review and evaluate published evidence for whether neosporosis in bulls may affect semen quality and production. N. caninum DNA can be detected by PCR in occasional batches of semen straws from bulls that are seropositive for N. caninum. Insemination of heifers with semen experimentally infected with 5 × 10⁴ N. caninum tachyzoites has caused persistent seroconversion in some animals. However, the highest concentration of parasites in the semen of naturally infected bulls was estimated, using quantitative PCR, as 10 tachyzoites. Thus it appears that, whether used for natural or artificial insemination, the semen of bulls naturally infected with N. caninum, does not contain the necessary intrauterine dose of tachyzoites to cause persistent seroconversion in a heifer or cow. Thus, based on the available evidence, the venereal transmission of N. caninum via bull semen is extremely unlikely. Nevertheless, neosporosis in bulls may influence semen quality and production. Epididymal semen concentration, viability, and motility appeared "to be" significantly decreased in N. caninum-seropositive bulls compared to seronegative bulls. Furthermore, semen production could be altered if neosporosis affects the thyroid gland. The thyroid hormones such as triiodothyronine and thyroxine (T4) may affect testicular development. Significantly lower concentrations of T4 were observed in the blood of N. caninum-seropositive, compared with those of seronegative bulls. Longitudinal studies are needed to confirm the long-term effect and significance of neosporosis on semen quality and thyroid hormone concentrations in bulls.

Neospora caninum infection in Iran (2004-2020): A review

Knowledge on neosporosis and associated risk factors in different species of animals are so important for designing the control programs and reduce the economic losses globally. This literature review targeted for evaluating the infection rate of Neospora caninum in animals in Iran. Until April 2020, all of published documents in the main English and Persian-language databases were searched. A total number of 110 documents (English = 85 and Persian = 25) were extracted. Most of reports were sero-epidemiological studies using ELISA in Iranian cattle population. The range of Neospora infection was 3.8–76.2% in cattle, 0–54.6% in dogs, 0.9–9.9% in sheep, 6.2% in goats, 19.2–55.9% in buffaloes, 20–42.2% in horses, 52% in donkeys, 3.2–27% in camels, 14% and 19% in cats, and 0–20.4% in rodents. This rate in birds was 17.3% in chicken, 9.8% and 30.4% in pigeons, 2.8% and 3.7% in sparrows, and 9.9% in hooded crows. This is a comprehensive literature review on Neospora infection in Iran at the first time. The infection of N. caninum is widespread in Iran especially in dogs and cattle population. This review can provide baseline information for future research. Study on other hosts especially on wild and exotic animals is recommended for exact estimate of neosporosis in Iran. Investigations into molecular diagnosis and genotyping of N. caninum strains are also needed; this will be helpful for developing vaccines and finding the connection among wild and domestic cycles of disease. Education on the risk factors associated with N. caninum infection for is suggested farmers and rural public.