Shelter cats host infections with multiple Trypanosoma cruzi discrete typing units in southern Louisiana

Abstract

Trypanosoma cruzi is a zoonotic parasite endemic in the southern US and the Americas, which may frequently infect dogs, but limited information is available about infections in cats. We surveyed a convenience sample of 284 shelter cats from Southern Louisiana to evaluate T. cruzi infection using serological and PCR tests. Parasites from PCR positive cats were also genotyped by PCR and deep sequencing to assess their genetic diversity. We detected a seropositivity rate for T. cruzi of at least 7.3% (17/234), and 24.6% of cats (70/284) were PCR positive for the parasite. Seropositivity increased with cat age (R² = 0.91, P = 0.011), corresponding to an incidence of 7.2% ± 1.3 per year, while PCR positivity decreased with age (R² = 0.93, P = 0.007). Cats were predominantly infected with parasites from TcI and TcVI DTUs, and to a lesser extent from TcIV and TcV DTUs, in agreement with the circulation of these parasite DTUs in local transmission cycles. These results indicate that veterinarians should have a greater awareness of T. cruzi infection in pets and that it would be important to better evaluate the risk for spillover infections in humans.

Keywords: Cat; Chagas disease; Discrete typing units; Genotyping; Phylogeny; Transmission cycle.

Figure 1

Seropositivity and PCR positivity according to cat age. Seropositivity significantly increased with cat age according to the following equation: Seropositivity = −0.069 + 0.072 * log(Age), P = 0.011, R² = 0.91. Conversely, PCR positivity significantly decreased with cat age according to: PCR positivity = 0.499 − 0.083 * log(Age), P = 0.007, R² = 0.93.

Figure 2

Phylogenetic analysis of T. cruzi sequences from cats. Maximum likelihood analysis of sequences from cats is shown, together with mini-exon sequences from reference T. cruzi strains from the indicated DTUs (TcI to TcVI and Tc bat). Bootstrap support is indicated only for the main nodes of the tree for clarity. Reference sequences are indicated with an asterisk.

Figure 3

Comparison of parasite sequences from cats with other mammalian hosts and vectors from southern Louisiana. Maximum likelihood phylogenetic trees are shown for TcI (A), TcII, TcV and TcVI (B) and TcIV DTUs (C). Only bootstrap node support > 50% is indicated for clarity. Cartoons illustrate species harboring the respective parasite DTUs. Reference sequences are indicated with an asterisk.