Quails are resistant to infection with Neospora caninum tachyzoites

The aim of this study was to characterize the role of quails (Coturnix coturnix japonica) as intermediate hosts for Neospora caninum. Fifty-eight 20-day old quails were individually identified with numbered rings and kept in cages adequate for the species. The birds were fed commercial feed and distilled water ad libitum. They were weighed daily during the first month and every seven days from then on. The birds were randomly distributed into 3 groups; 40 quails (group A) and 8 quails (group B) received 3.5 × 106 and 5 × 106N. caninum tachyzoites, respectively, and 10 quails (group C) received placebo. Four quails from group A and one from group C had their blood collected and were euthanized on the 1st, 3rd, 5th, 7th, 14th, 21th, 30th, 60th, 120th day after infection (DAI), and 4 quails from group B were euthanized on days 60th and 120th DAI. Following euthanasia, the birds were submitted to necropsy, the organs were weighed and fragments were collected for histopathology, immunohistochemistry (IHC) and PCR. On the 60th DAI, two dogs were fed tissue obtained from group A quails, and one dog was fed quail tissues from group B. The dogs' blood was collected weekly for serology, and their feces were collected daily for 33 days for microscopy and molecular identification of oocysts. Student's t-test was used to compare the weights of the collected organs and the quail and cloacal temperature. No quail presented any clinical signs or died. Splenomegaly and hepatomegaly were the primary necropsy findings during the first week of infection (p < 0.05). Positive serology, immunoreactivity through IHC and molecular identification of the parasite, were observed, especially during the first two weeks of infection. No dogs eliminated the oocysts or seroconverted. The infected quails gained more weight than the control quails. The results demonstrated that quails are resistant to infection with N. caninum tachyzoites under the conditions of this study.