Ahead of Print - Absence of Neospora caninum DNA in Human Clinical Samples, Spain - Volume 25, Number 6—June 2019 - Emerging Infectious Diseases journal - CDC

Ahead of Print - Absence of Neospora caninum DNA in Human Clinical Samples, Spain - Volume 25, Number 6—June 2019 - Emerging Infectious Diseases journal - CDC

Volume 25, Number 6—June 2019

Research Letter

Absence of Neospora caninum DNA in Human Clinical Samples, Spain

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Research Letter

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Rafael Calero-Bernal , Pilar Horcajo, Marta Hernández, Luis Miguel Ortega-Mora, and Isabel Fuentes

Author affiliations: Complutense University of Madrid, Madrid, Spain (R. Calero-Bernal, P. Horcajo, L.M. Ortega-Mora); Carlos III Institute of Health, Madrid (M. Hernández, I. Fuentes)

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Abstract

Low antibody titers to Neospora caninum have been reported in humans, but infection has not been confirmed. We used N. caninum–specific PCR to test 600 clinical samples from patients with toxoplasmosis signs but Toxoplasma gondii–negative PCR results. We did not detect N. caninum DNA, demonstrating it is an unlikely opportunistic zoonotic agent.

The coccidian parasite Neospora caninum (Apicomplexa: Sarcocystidae) is a major abortifacient agent in ruminants, especially cattle. It is phylogenetically close to Toxoplasma gondii (1), a parasite of high prevalence in humans, but biologically different. N. caninum parasites have a restricted host range but can infect primates (2,3).

N. caninum infection causes neuromuscular disease in dogs and reproductive disorders in ruminants, causing fetal loss due to vertical transfer of parasites during acute infections or reactivation of chronic infections. Clinical neosporosis in animals resembles the disease outcome of toxoplasmosis (1).

N. caninum parasites have been successfully cultured in human cell lines, but low antibody titers of unconfirmed specificity against N. caninum have been reported in human serum samples (1,4,5). The significance of these findings is uncertain because neither parasite DNA nor viable parasites have been demonstrated in human tissues. Unconfirmed reports of N. caninum–specific antibodies in the human population (4,5) and few attempts to search for parasite DNA in human samples prompted us to test specifically for Neospora DNA in human clinical specimens and assess its possible role in human illness.