Self-Mating in the Definitive Host Potentiates Clonal Outbreaks of the Apicomplexan Parasites Sarcocystis neurona and Toxoplasma gondii

Tissue-encysting coccidia, including Toxoplasma gondii and Sarcocystis neurona, are heterogamous parasites with sexual and asexual life stages in definitive and intermediate hosts, respectively. During its sexual life stage, T. gondii reproduces either by genetic out-crossing or via clonal amplification of a single strain through self-mating. Out-crossing has been experimentally verified as a potent mechanism capable of producing offspring possessing a range of adaptive and virulence potentials. In contrast, selfing and other life history traits, such as asexual expansion of tissue-cysts by oral transmission among intermediate hosts, have been proposed to explain the genetic basis for the clonal population structure of T. gondii. In this study, we investigated the contributing roles self-mating and sexual recombination play in nature to maintain clonal population structures and produce or expand parasite clones capable of causing disease epidemics for two tissue encysting parasites. We applied high-resolution genotyping against strains isolated from a T. gondii waterborne outbreak that caused symptomatic disease in 155 immune-competent people in Brazil and a S. neurona outbreak that resulted in a mass mortality event in Southern sea otters. In both cases, a single, genetically distinct clone was found infecting outbreak-exposed individuals. Furthermore, the T. gondii outbreak clone was one of several apparently recombinant progeny recovered from the local environment. Since oocysts or sporocysts were the infectious form implicated in each outbreak, the expansion of the epidemic clone can be explained by self-mating. The results also show that out-crossing preceded selfing to produce the virulent T. gondii clone. For the tissue encysting coccidia, self-mating exists as a key adaptation potentiating the epidemic expansion and transmission of newly emerged parasite clones that can profoundly shape parasite population genetic structures or cause devastating disease outbreaks

Toxoplasma gondii antibodies sheep in Lages, Santa Catarina, Brazil, and comparison using IFA and ELISA Anticorpos toxoplásmicos em ovinos de Lages, Santa Catarina, Brasil, e comparação utilizando RIFI e ELISA

Toxoplasmosis in sheep is a disease of great importance in veterinary medicine, which causes economic losses in livestock and has a great impact on human health, since consumption of infected meat facilitates transmission of zoonotic infections. Blood samples from sheep (n = 360) were collected from 13 farm properties in the municipality of Lages, Santa Catarina, to estimate the prevalence of toxoplasmosis and identify risk factors associated with Toxoplasma gondii infection. T. gondii, antibodies were investigated by means of the indirect immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA). Animals infected with T. gondii were found on 100% of the farms. IFA detected 56.9% (205/360) and ELISA 42.5% of the infected sheep. Breed was the only risk factor associated with the presence of T. gondii antibodies. ELISA showed sensitivity of 61%, specificity of 82% and kappa of 0.41, which was considered moderate. This allows use of ELISA as an alternative technique for diagnosing T. gondii in sheep.<br>A toxoplasmose ovina é uma doença parasitária de elevada importância em medicina veterinária e em saúde pública, acarretando prejuízos na produção animal, gerados pelas perdas reprodutivas e econômicas, além de sua implicação na saúde humana, já que o consumo de carne infectada facilita a transmissão zoonótica. Para determinar a prevalência e identificar fatores de risco para a infecção por T. gondii em ovinos de Lages, Santa Catarina, amostras de sangue (n = 360) foram coletadas em 13 propriedades. Cada criador respondeu a um questionário para permitir a identificação dos fatores de risco da infecção. A pesquisa de anticorpos foi realizada por meio da Reação de Imunofluorescência Indireta (RIFI > 64) e do Ensaio Imunoenzimático Indireto (ELISA). Em 100% das propriedades foram encontrados animais positivos. Pela RIFI, 205 (56,94%) ovinos apresentaram anticorpos contra T. gondii e pelo ELISA, 153 (42,50%). Considerando-se as técnicas sorológicas e a análise estatística, foram fatores de risco pelo ELISA: a idade, a fonte de água e a categoria animal; e pela RIFI, o tipo racial. Foi constatada sensibilidade de 61%, especificidade de 82% e concordância Kappa de 0,41 entre o ELISA e a RIFI (1:64), considerada moderada, permitindo indicar o ELISA como técnica adequada para o diagnóstico de T. gondii na espécie ovina

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

BACKGROUND: Toxoplasma 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. METHODS: Hearts 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). RESULTS: Overall, 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. CONCLUSIONS: The 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