A Comparison of Antiserum and Protein A as Secondary Reagents to AssessToxoplasma gondiiAntibody Titers in Cats and Spotted Hyenas

Abstract

Toxoplasma gondii is a protozoal parasite with worldwide distribution that is able to infect a wide variety of mammals and birds. Our main goal was to screen for T. gondii antibody titers in a previously untested species, the spotted hyena ( Crocuta crocuta); however, this goal first required us to investigate serological procedures that could be suitable for hyenas. Cats are the closest domestic relations of hyenas, so T. gondii antibody titers were first compared in 26 feral cats with specific or nonspecific fluorophore-labeled secondary reagents, i.e., anti-cat IgG or protein A. Substitution of anti-cat IgG with protein A caused a statistically significant drop in titer measurements in cats (P = 0.01) with a reduction of the geometric mean titer equivalent to 1 doubling-dilution. The same procedures were then applied to captive spotted hyenas. Titers measured in 9 of 10 hyenas were identical whether anti-cat IgG or protein A was used as the secondary reagent: 5 had titers <1:16, 2 had titers of 1:16, and 2 had titers of 1:32. One hyena had maximum titers of 1:64 or 1:32 when anti-cat IgG or protein A was used, respectively. The use of protein A as the secondary reagent in serologic assays can be applied to a range of mammalian species and seems unlikely to affect test specificity; however, the use of protein A may reduce test sensitivity, as suggested in the present study using cats. Despite a control program, some exposure to T. gondii had occurred in the Zoo's spotted hyenas.

Evidence of high exposure to Toxoplasma gondii in free-ranging and captive African carnivores

“…(1980)Brown hyenaZoos in Czech Republic3/3 (100)IFASedlak and Bártová (2006)Striped hyenaZoo in France1/2 (50)MATAlerte (2008)Spotted hyenaZoo in France1/1 (100)MATAlerte (2008)Striped hyenaBreeding Centre for Endangered Arabian Wildlife, UAE3/6 (50)MATDubey et al. (2010)Spotted hyenaZoos in Australia5/10 (50)IFAWait et al. (2015)…”

Toxoplasma gondii infections are associated with costly boldness toward felids in a wild host

“…We treated these individuals as negative in our analyses, following protocols from other recent studies 22 . Although ELISAbased assays performed relatively well in prior studies of T. gondii in both hyenas 31 and other mammals 22 , the method can also be sensitive to cross-reactivity with antibodies to other, related parasites 32 . We therefore retested 60 randomly chosen plasma samples using an alternative, indirect fluorescence agglutination test (IFAT), which is less sensitive to cross reactivity 31 , in order to confirm that the two methods yielded similar results using our plasma samples (Supplementary Fig.…”