CONICET | Buscador de Institutos y Recursos Humanos

Toxoplasmosis is a parasitic disease caused by the Apicomplexan parasite Toxoplasma gondii. This intracellular protozoan is worldwide distributed, infecting a broad range of birds and mammals, including humans. Toxoplasma gondii is considered one of the most common causes of reproductive failure in sheep. In Argentina, a case of abortion due to T. gondii has been reported in a sheep flock raised for meat production. Furthermore, Toxoplasma genotypes present in Argentinean sheep flocks have not been published yet. The objectives of the present study are to describe an outbreak of T. gondiiabortions in a dairy sheep flock from Argentina and to do the molecular characterization of the genotype of T. gondii involved. Between May and June 2020, one hundred and seventeen sheep aborted in a dairy flock of 633 sheep located in Pehuajó, Buenos Aires province, Argentina. Thirty-three foetuses and placentas were recovered and submitted to the Specialized Veterinary Diagnostic Service (SDVE) of INTA Balcarce, in order to establish an etiological diagnosis. These tissues were examined by standard gross pathology procedures and were tested using serology, histopathology and immunohistochemistry. Moreover, DNA was obtained from foetal tissues and a PCR assay on the B1 gene was used to detect T. gondii. Toxoplasma genotyping by nested PCR-RFLP was performed over the positive PCR samples. In addition, milk (n=63) and blood samples (n=207) were obtained from sheep (aborted and non-aborted) for serological and PCR analysis. Compatible histological lesions with toxoplasmosis including encephalitis, pneumonia, and severe multifocal necrotizing placentitis were observed. Toxoplasma gondii was immunolabeled in placenta, brain tongue, intestine, lung, and liver. Antibodies against T. gondii and DNA were detected in 33/33 foetal fluids and in 30/33 brain samples, respectively. Preliminary genotyping analysis using the molecular markers SAG1 and 5´-3´SAG2 identified the Type II allele. Toxoplasma gondii-seroprevalence was 93.47% (193/207) with end-point titres higher than 1/12.800 in some sheep. Although 92.06% (58/63) of the analysed milk samples from aborted sheep evidenced antibodies against T. gondii, Toxoplasma-DNA was not found in any of these samples. No evidence of other abortifacient infectious agents were detected in the aborted foetuses. Scarce information of T. gondii-abortion outbreaks has been published in Argentina, being this study the first Toxoplasma-genotyping of a natural case. Further Investigations at a larger scale are required to continue providing detailed information about the T. gondii genotypes involved the reproductive failure that will allow us to better understand the epidemiology of T. gondii in Argentina.