Evaluation of Cross Immunity and Histopathological Findings in Experimentally Infected BALB/c Mice with Neospora caninum and Besnoitia caprae

Abstract

Background: Caprine besnoitiosis is an economically important disease of goats. Neospora caninum, another coccidian parasite of worldwide distribution, infects several animal species and is a major cause of abortion in cattle. Combined infections of N. caninum and Besnoitia caprae can occur in geographical areas endemic for both species of parasite in goats. This experiment was conducted to investigate the possible cross-immunity between these two infections in experimentally infected BALB/c mice.

Methods: Forty BALB/c mice were divided into four equal groups. The mice of Groups 1 and 4 were inoculated with 1×10(6) live virulent tachyzoites of N. caninum (NC-1), while animals of Groups 2 and 3 were inoculated with sterile tissue culture medium. Each mouse in Groups 1 and 2 was challenged 28 days later with 1×10(6) live virulent bradyzoites of B. Caprae (BC-1).

Results: Following the challenge, the mice in Groups 1 and 2 showed 100% morbidity and 100% mortality within 9 days post infection, while all the animals of Groups 3 and 4 remained alive. The dead animals were necropsied. The survivors (mice in Group 3 and 4) were euthanized 9 days after inoculation and the gross and histopathological lesions in different organs were investigated.

Conclusion: Immunization and challenge experiments with lethal dose of B. caprae in the highly susceptible BALB/c mice showed no cross-protection between N. caninum and B. caprae.

Keywords: BALB/c mice; Besnoitia caprae; Cross reaction; Neospora caninum.

Fig. 1

A histopatholgy section from the lungs of an animal of Group 1. Hyperemia, hemorrhages and interstitial pneumonia with mononuclear cell infiltration (arrows) are seen in the lung section (H and E, scale bar = 20 µm)

Fig. 2

Brain section from a mouse of Group 2. Mild gliosis is evident (arrow) (H and E, scale bar = 20 µm)

Fig. 3

Perivascular cuffing (arrow) with hyperemia is seen in brain section of a mouse of Group 2 (H and E, scale bar = 85 µm)

Fig. 4

Higher magnification of Fig. 3. PVC (perivascular cuffing) (H and E, scale bar = 20 µm)