Introduction

Toxoplasmosis is a worldwide parasitic zoonosis produced by Toxoplasma gondii. In immunocompetent individuals, the primary infection is usually asymptomatic, but persists in a latent state throughout life, and can be reactivated in case of immunosuppression ¹. The Feline is the definitive host eliminating oocysts in the feces. The mechanisms of human infection are the ingestion of oocysts, blood transfusion, organ transplants and by placental transmission ^1-4. Worldwide, the prevalence of toxoplasmosis is high. In the Americas, around 65% of the population has detectable levels of total anti-Toxoplasma gondii specific immunoglobulins, where contact with feces of cats has been shown to be the main risk factor ².

In Venezuela, studies conducted in pregnant women, children and adults at risk (homeless), blood donors and native populations, show a high frequency of specific IgG against T. gondii^5-14. However, because it is not a mandatory reporting disease, there is a sub-registration ¹⁵. The aim of this study was to evaluate the seroprevalence of IgG and IgM anti-T.gondii in women of the Coro in 2008 and 2012.

Methods

Design and sample: A comparative study was conducted with 2008 and 2012 data. 522 women from Coro city, randomly selected, participated in the study and a serum sample were collected.

Ethical considerations: All women voluntarily accepted their participation through the signed informed consent. Anonymity and the World Bioethics Congress guidelines as well as Helsinki declaration were preserved.

Technical information: IgG and IgM anti-Toxoplasma gondii detection in 2008 (n=268) was made by the Microparticle Enzyme Immunoassay (MEIA), using the commercial kit (Toxo IgG and Toxo IgM, AxSYM®assay Abbott), and in 2012 (n=254) with the Fluorescent Enzyme-Linked Assay (ELFA), following the protocol of the manufacturer (VIDAS TOXO IgG and IgM system of bioMerieux®Inc). The reference values of the commercial kit were considered as a diagnostic. The MEIA kit reference values for IgG: positive >2.5 IU/ml and lower negative. For IgM: positive >0.600 IU/ml, negative <0.499 IU/ml and indeterminate 0.500-0.599 IU/ml. The ELFA kit reference values for IgG: positive >8 IU/ml and negative less than 4 IU/ml and indeterminate between 4-8 IU/ml. For IgM: positive >0.65 IU/ml, negative <0.55 IU/ml and indeterminate 0.55-0.65 IU/ml. Any indeterminate sample was repeated to confirm the results.

Analysis of the data: Data obtained was entered on to an excel spreadsheet and transferred to SPSS version 21 statistical program for the analysis.

Result

Of the 522 women evaluated, 86% (n=451) were seronegative anti-Toxoplasma gondii specificity IgG-/IgM-. 13% (n=65) presented IgG+/IgM-. 1% was IgG-/IgM+ (n=2) and 1% was IgG+/IgM+ (n=4). The seroprevalence by year and specificity are shown in Table 1. Women who presented seropositivity to IgM received pharmacological treatment. The distribution according to the specificity of IgG/IgM antibody is shown in Figure 1.

Figure 1
anti-Toxoplasma gondii IgG-IgM specificity distribution. 2008-2012. Coro. Venezuela

Discussion

Toxoplasmosis is the most widespread parasitic zoonosis in nature. It has been shown in all latitudes, in humans, more than 300 species of mammals and around 30 species of birds. It is usually asymptomatic, but it is responsible for many abortions, fetal, perinatal and infant hazard and is the most frequent cause of focal infection of the central nervous system in patients with AIDS, representing a latent threat for all immunosuppressed patients ^2-4.

We found 13% of seropositivity of anti-T gondii IgG+/IgM-, keeping low thru the years. No statistically significant variation (p>0.05) during the follow-up. Positivity both for IgG/IgM was observed only in 0.7% of the 2012 samples, probably a reactivation of a past infection and was 0% on the 2008 samples (Table 1). Our data is in contradiction of the studies in Venezuela how show a high prevalence of specific IgG/IgM antibodies in urban areas between 32 ^5,6 and 61%, in pregnant women and in individuals at risk (homeless) between 42 and 67% ^7-9. In rural areas it has been reported from 39 to 49% ¹⁰. In native populations: 50% of the Barí of the Sierra de Perijá of Zulia state, 88% of the Güajiba from the Venezuelan Amazon rainforest and 69% from the Piaroa of the Bolívar state ^11-14. High prevalence rates are also observed in the rest of the Americas: Brazil 66%, Colombia 47%, Mexico 56%, Trinidad and Tobago 39% ^16-19. In Europe, 38% in Croatia ²⁰. In Asia, 42% to 55% in India, Malaysia and Nepal ^21,22.

The IgM seroprevalence remained less than 1% during the years, which shows a very low prevalence of acute infection in this population ^23,24. This low prevalence is also observed in a small group with no pregnant women in Oman ²⁵. It also proves that both diagnostic techniques (ELFA and MEIA) provide good reproducibility of the results and comparable sensitivity and specificity at the quantitative level of IgG/IgM specific anti-T. gondii (Fig 1). The specific IgG/IgM reactivity it is easier to evaluate the stage of the infection since high IgG levels can persist beyond the year and even low levels can remain in past infections. However, a low titer may also be the first stage in the ascending curve of IgG in a recent infection ^26,27.

The lower frequency of infection by T. gondii found in this study comparative with others carried out in the country could be due to the climate characteristics of the Coro city, with high temperatures (24-34ºC), clay soils of acidic pH (4,5-5,5) and strong trade alisios winds ²⁸, which probably affect the viability of the oocysts, decreasing the possibility of transmission.

We recommend keeping the follow-up of the seroprevalence of infection by T. gondii in Venezuela, with the evaluation of the risk factors in the infected people and to study if the environmental characteristics may have consequences of the on the viability of the oocysts.

Acknowledge

To the staff of the laboratories “Virgen María Auxiliadora” and IVSS "Dr. Rafael Gallardo” for all the support and Dr. Rosaura Hernández for the critical review of the manuscript.

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Notas de autor

Autor de Correspondencia: Martínez Méndez Dilia. Talatona Clinic. International SOS. Luanda. Angola. Rua S10. Sector de Talatona. Zona CC-B2. Luanda. Angola. Telephone: +34622339081 & +244 936174795. E-mail: dkmartinez.mw@gmail.com