Predominance of atypical genotypes of Toxoplasma gondii in free-roaming chickens in St. Kitts, West Indies

Clare M Hamilton,Chunlei Su,Tatiana M Corey,Elisabeth A Innes,Kenneth Boey,Hieuhanh Huynh,Frank Katzer,Isabelle Villena,Patrick J Kelly,Deidra Metzler

doi:10.1186/s13071-017-2019-6

Abstract

BackgroundToxoplasma gondii is a worldwide protozoan parasite of felids which can infect almost all warm-blooded animals, including humans. Free-roaming chickens are good indicators of environmental contamination with T. gondii oocysts because they feed from the ground. Previous research has demonstrated a high seroprevalence of T. gondii in domestic animals on St. Kitts but little is known about the genotypes circulating in the environment.MethodsHearts and brains from 81 free-roaming chickens in St. Kitts were digested and inoculated into 243 Swiss Webster mice in a bioassay. DNA was extracted from digested chicken tissues and the brains of all mice, and screened for T. gondii. Positive samples were genotyped using restriction fragment length polymorphism. Chicken sera were also screened for T. gondii antibodies using a modified agglutination test (MAT).ResultsOverall, 41% (33 out of 81) of chickens were positive for T. gondii either by serology and/or by PCR. Antibodies to T. gondii were detected by MAT in 32% (26 out of 81) of chickens, and T. gondii DNA was detected in mouse brains representing 26% (21 out of 81) of chickens. Genotyping of 21 DNA isolates, using polymorphisms at 10 loci, including SAG1, SAG2 (5′-3′ SAG2 and alt.SAG2), SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico, revealed that 7 were ToxoDB genotype #141, 6 were #1 (Type II), 3 were #13, 3 were #265, one was #264 and one was #2 (Type III). Genotypes #13 and #141 appear to be more virulent.ConclusionsThe results of this study highlight the greater genetic diversity of T. gondii circulating in the Caribbean region, with potentially different degrees of virulence to humans.

Highlights

Toxoplasma gondii is a worldwide protozoan parasite of felids which can infect almost all warmblooded animals, including humans
Overall, 33 out of 81 (41%) chickens were positive for T. gondii either by serology (MAT-positive) and/or by ITS1 PCR, whereby T. gondii DNA was detected either in digested chicken tissues or in the brain tissues of inoculated mice (Table 1)
Antibodies to T. gondii were detected by modified agglutination test (MAT) in 32% (26 of 81) of chickens, with titres of 1:6 in 10, 1:10 in 5, 1:25 in 3, 1:50 in 4, 1:100 in 1, 1:400 in 1, 1:800 in 1, and 1:3200 in 1 chicken (Table 1)

Summary

Introduction

Toxoplasma gondii is a worldwide protozoan parasite of felids which can infect almost all warmblooded animals, including humans. Free-roaming chickens are good indicators of environmental contamination with T. gondii oocysts because they feed from the ground. Toxoplasma gondii is a parasite of felids which can infect almost all warm-blooded animals, including humans [1]. Free-roaming chickens are considered one of the most important hosts for studying the epidemiology of T. gondii because they feed from the ground and are good indicators of environmental contamination with oocysts [10]. Strains of T. gondii have been characterized from free-roaming chickens in South America [9], Central America [11], the Caribbean [12], Asia [13], Africa [14] and Europe [15], and it is becoming apparent that isolates from South America, in particular Brazil, are genetically distinct [16]

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Results

Conclusion