Economic and public health importance of Toxoplasma gondii infections in sheep: 2009-2020.

Toxoplasma gondii infections are common in humans and animals worldwide. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, control, and genetic diversity of T. gondii in sheep in the past decade. There is debate and uncertainty concerning repeat congenital infection as evidenced by finding T. gondii DNA in progeny of chronically infected sheep. However, there is no concrete evidence that T. gondii is the cause of repeated abortions in sheep. Recent data concerning pathogenesis of abortion in acutely infected sheep are reviewed. PCR-RFLP typing of T. gondii DNA derived from viable T. gondii isolates or tissues of infected sheep revealed low genetic diversity in sheep in Europe, Africa, Asia and North America but high diversity in South America. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Public health and economic importance of Toxoplasma gondii infections in goats: The last decade.

Toxoplasma gondii infections are common in humans and animals worldwide. Toxoplasmosis in goats continues to be of public health and economic concern. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, treatment, and genetic diversity of T. gondii in goats in the past decade. There is debate and uncertainty regarding excretion of T. gondii in milk and the ingestion of raw milk as sources of T. gondii infection for humans. Toxoplasmosis can cause abortion and deaths even in adult goats. PCR-RFLP typing of T. gondii DNA derived from viable T. gondii isolates has revealed genetic diversity in goats in North and South America. The significance of T. gondii isolates in domestic goats usually associated with wildlife in USA is discussed. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

The design of a Social Cost-Benefit Analysis of preventive interventions for toxoplasmosis: An example of the One Health approach.

Toxoplasma gondii infections cause a large disease burden in the Netherlands, with an estimated health loss of 1,900 Disability Adjusted Life Years and a cost-of-illness estimated at €44 million annually. Infections in humans occur via exposure to oocysts in the environment and after eating undercooked meat containing tissue cysts, leading to asymptomatic or mild symptoms, but potentially leading to the development of ocular toxoplasmosis. Infection in pregnant women can lead to stillbirth and disorders in newborns. At present, prevention is only targeted at pregnant women. Cat vaccination, freezing of meat destined for undercooked consumption and enhancing biosecurity in pig husbandries are possible interventions to prevent toxoplasmosis. As these interventions bear costs for sectors in society that differ from those profiting from the benefits, we perform a social cost-benefit analysis (SCBA). In an SCBA, costs and benefits of societal domains affected by the interventions are identified, making explicit which stakeholder pays and who benefits. Using an epidemiological model, we consider transmission of T. gondii after vaccination of all owned cats or cats at livestock farms. To identify relevant high-risk meat products that will be eaten undercooked, a quantitative microbial risk assessment model developed to attribute predicted T. gondii infections to specific meat products will be used. In addition, we evaluate serological monitoring of pigs at slaughter followed by an audit and tailor made advice for farmers in case positive results were found. The benefits will be modelled stochastically as reduction in DALYs and monetized in Euro's following reference prices for DALYs. If the balance of total costs and benefits is positive, this will lend support to implementation of these preventive interventions at the societal level. Ultimately, the SCBA will provide guidance to policy makers on the most optimal intervention measures to reduce the disease burden of T. gondii in the Netherlands.

Break-even analysis of costs for controlling Toxoplasma gondii infections in slaughter pigs via a serological surveillance program in the Netherlands.

Toxoplasma gondii (T. gondii) is a food safety hazard which causes a substantial human disease burden and cost-of-illness. Infected pig meat is a common source of toxoplasmosis. A break-even analysis was conducted to estimate the point for which the intervention cost at fattening pig farms equaled the cost of averted human disease burden and cost-of-illness minus the costs of a T. gondii surveillance program. The surveillance program comprised serological testing of blood samples taken at slaughter. Break-even points were determined given alternative levels of the effectiveness of the intervention program (10% up to 90% in steps of 10%), the value of an averted DALY (20,000, 50,000 and 80,000 Euro), and threshold of sample prevalence for a farm to be under intervention (5% up to 50% out of 20 samples in steps of 5%). Since test characteristics are a determining factor in the break-even analysis, and literature is inconclusive concerning sensitivity (se) and specificity (sp) of the serological test kit used, two alternative sets of assumptions were analysed. The estimated maximum costs of an intervention if only benefits for domestic consumers were accounted amounted approximately 2981 Euro (se=98.9% and sp=92.7%) versus 4389 Euro (se=65.2% and sp=97.4%) per year per fattening pig farm under intervention assuming an effectiveness of 50%, 50,000 Euro per averted DALY and threshold T. gondii sample prevalence of 5% for a farm to be under intervention. Since almost 80% of the gross domestic production is exported corresponding break-even values increased up to 12,034 Euro and 18,366 Euro if benefits for consumers abroad were included as well. Empirical research to strengthen the knowledge about the efficacy of a farm intervention measures is recommended.

Toxoplasma gondii em suínos com ênfase na contribuição brasileira: [revisão] / Toxoplasma gondii in swine with emphasis in Brazilian contribution: [review]

Objetivos: revisar a literatura nacional referente aos principais dados de estudos de toxoplasmose sobre a epidemiologia, patologia e imunologia, frequência de anticorpos e isolamento do parasito em suínos, e as literaturas nacional e internacional sobre avaliação molecular de cepas isoladas de suínos. Fonte de dados: foram pesquisadas as bases de dados Scielo, Scopus, Science Direct e Google Scholar. Síntese dos dados: a toxoplasmose em suínos apresenta alta prevalência sorológica e de identificação do parasito, por isolamento ou detecção de DNA, em grande parte do território nacional, causando problemas neurológicos, reprodutivos e econômicos e aumentando o risco de transmissão para a população humana. As principais fontes de infecção para os suínos ainda são os gatos errantes, responsáveis pela disseminação e adaptação do parasito a novos hospedeiros e condições de sobrevivência alternativas. A biologia molecular trouxe grande contribuição, não somente para a detecção em amostras de animais mortos, mas, principalmente, na elucidação do comportamento evolutivo do parasito na espécie suína. Conclusões: a toxoplasmose em suínos é um problema real tanto na criação como produção de alimentos, o que resulta em grave problema econômico e de saúde pública. Apresenta prevalência variável em suínos no mundo e alta variabilidade genotípica, principalmente na América do Sul.

Aims: To review the national literature of toxoplasmosis about epidemiology, pathology, immunology, antibody frequency and parasite isolation in swine, and the national and international literature on molecular evaluation of strains isolated from swine. Source of data: Survey was performed in Scielo, Scopus, Science Direct and Google Scholar databases. Summary of findings: Toxoplasmosis in swine presents high serological prevalence and parasite identification by isolation or DNA detection, is widely distributed in national territory, causing neurological, reproductive, and economical problems, and increases the risk of transmission to human population. Errant cats, which are the main source of infection to swine, are responsible for the dissemination and adaptation of the parasite to new hosts and alternative survival conditions. Molecular biology contributed significantly to the parasite detection in samples from dead animals and, particularly, in the elucidation of the parasite evolutional behavior in swine species. Conclusions: Toxoplasmosis in swine is a real problem in both breeding and food production, becoming a serious problem to public health. It presents a variable prevalence in swine around the world, and presents high genotypic variability, particularly in South America.

The incidence and economic significance of ovine toxoplasmosis in Uruguay.

Antibodies to Toxoplasma gondii were measured before and after pregnancy in a 1:64 dilution of sera with the direct agglutination test in 1613 ewes from 18 farms in eight different counties of Uruguay from 1992 to 1994. The overall seroprevalence increased from 28.7% before mating to 38.5% after lambing in 2.5 years and thus the incidence was 9.8%. Losses due to toxoplasmosis during pregnancy were estimated to be 1.4-3.9% of the total number of ewes investigated, amounting to approximately US$1.4-4.7 million for the whole country.

Experimental toxoplasmosis in broiler chicks.

To evaluate chicken toxoplasmosis both as an economic and a public health subject, 84 broiler chicks of a commercial strain, 30 days old, were distributed into seven groups of 12 birds (three replications of four chicks) experimentally infected with three developing T. gondii stages of the P strain as follows: tachyzoites, intravenous (two groups: 5.0 x 10(5) and 5.0 x 10(6)), cysts, per os (two groups: 1.0 x 10(2) and 1.0 x 10(3)) and oocysts, per os (three groups: 5.0 x 10(2), 5.0 x 10(3) and 5.0 x 10(4)). Twelve chicks received only a placebo (control group). During the next 30 days the following parameters were estimated: productivity (weight gain and feed conversion), clinical signs, including rectal temperature and parasitemia (bioassay). No clinical signs suggesting toxoplasmosis were seen and no statistical differences on productivity standards were found in comparison between inoculated and control chicks. However, fowls inoculated with tachyzoites and oocysts occasionally showed hyperthermia. Some haematological changes were detected in fowls inoculated with T. gondii. Anatomo-histopathological changes were not observed. From 14 parasitemias detected, 35.7% appeared on the 5th day after inoculation and 57.1% of them resulted from oocysts inoculation. After 30-35 days all birds were slaughtered: fragments from 12 organs or tissues from each of them were subjected to artificial peptic digestion and after that injected into T. gondii antibody-free mice (IIFR). T. gondii was detected in brain (12), pancreas (five), spleen (five), retina (five), kidney (two), heart (four), proventriculus (three), liver (two), intestine (two), lung (one), and skeletal muscle (one). Similar to observations with parasitemia, from 42 T. gondii isolations, 59.5% came from chicks which had received oocysts. It can thus be inferred that the developing form, expelled by cats, is the most important for T. gondii chicken infection and that brain is the most infected organ in birds. Attention must be paid to the potential importance of chicken meat in public health, since T. gondii was isolated from skeletal and heart muscles.

The incidence and economic significance of ovine toxoplasmosis in Uruguay.

Antibodies to Toxoplasma gondii were measured before and after pregnancy in a 1:64 dilution of sera with the direct agglutination test in 1613 ewes from 18 farms in 8 different counties of Uruguay from 1992 to 1994. The overall seroprevalence increased from 28.7% before mating to 38.5% after lambing in 2.5 yr and thus, the incidence was 9.8%. Losses due to toxoplasmosis during pregnancy were estimated to be 1.4 to 3.9% of the total number of ewes investigated, amounting to approximately US$1.4-4.7 million for the whole country.

Evaluación de las pérdidas económicas debidas a toxoplasmosis en ovinos en el Uruguay / Evaluation of economic losses due to sheep toxoplasmosis in Uruguay

Se determinó la presencia de anticuerpos contra Toxoplasma gondii, antes y después de la gestación, con la reacción de aglutinación directa para toxoplasmosis (AD), en 1613 ovejas de 18 establecimientos de diferentes Departamentos del Uruguay, de 1992 a 1994. La prevalencia total de la infección ascendió de 28,7 por ciento antes de la gestación a 38,5 por ciento, luego de la misma. La incidencia fue, por lo tanto de 9,8 por ciento. Las pérdidas debidas a la infección toxoplásmica durante la gestación se estimaron teóricamente con una fórmula que contempla el nivel de incidencia así como algunos factores de la patogénesis de la enfermedad en el ovino. Sobre esta base, de 1,4 a 3,9 por ciento del total de las ovejas investigadas pudieron haber perdido sus corderos debido a la toxoplasmosis. Esto representa una pérdida económica anual para la industria ovina en el Uruguay de 1,9 a 5,2 millones de dólares americanos. En la estación de parición de 1993, de 562 ovejas y borregas que fueron servidas en uno de los establecimientos. 154 tuvieron corderos y 125 abortaron. Se aisló Toxoplasma mediante bioensayos, a partir de los fetos abortados. Veintiocho sueros de ovejas que abortaron presentaron títulos de 1:16.384 o mayores con el test de AD. Se apreciaron puntos blancos de necrosis del tamaño de la cabeza de un alfiler sobre la superficie de los cotiledones placentarios de las ovejas que abortaron. Los hallazgos histopatológicos fueron necrosis y calcificación de las vellosidades cotiledonarias y encefalitis, hepatitis y neumonía. Seis meses luego de los abortos, 55,6 por ciento de 300 ovejas presentaron títulos de 1:1.024 o mayores, reflejando la extensión de la infección. Se detectaron abortos toxoplásmicos en otros establecimientos, el mismo año. Se destaca la situación de subdiagnóstico de la toxoplasmosis ovina, al quedar enmascarada por otras causas de pérdidas de corderos más extensivos, salvo que adopte la magnitud inusual del caso relatado

Economic and public health considerations of congenital toxoplasmosis in lambs.

Congenital toxoplasmosis was diagnosed in a flock of Hampshire sheep in South Dakota. The 80 ewes produced 144 lambs, 30 of which were born dead; toxoplasmosis was diagnosed in 11 of the dead lambs. The remaining 114 lambs grew normally, but 68 (40.3%) had agglutinating Toxoplasma gondii antibodies. Modified agglutination test T gondii antibody titers for 114 lambs were: less than 100 (n = 46), 64 (n = 2), 256 (n = 1), 1,024 (n = 12), and greater than or equal to 4,096 (n = 53). Tissues of 8 seropositive lambs were bioassayed for T gondii tissue cysts. Toxoplasma gondii was isolated from the tongue and lamb chops of 7, heart of 3, and legs of lamb of all 8 lambs.

A review of toxoplasmosis of animals in the U.S.S.R.

Information on the serologic and parasitologic prevalence of Toxoplasma gondii infection in domestic and wild animals of the U.S.S.R. is reviewed. Although complement-fixing antibodies to T. gondii were widely prevalent in animals, little information is available on the presence of viable T. gondii in tissues of animals. Reports of epizootics in which T. gondii was suspected to be the causative agent of toxoplasmosis are summarized. Also, the strict economic impact of toxoplasmosis on agriculture in the U.S.S.R. needs evaluation.