Abstracts

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Prevalence of IgG antibodies specific to Toxoplasma gondii among blood donors in Recife, northeast Brazil

Prevalência de anticorpos IgG específicos anti Toxoplasma gondii em doadores de sangue no Recife, nordeste do Brasil

Raquel A.L. Coêlho^I; Masashi Kobayashi^II; Luiz B. Carvalho Jr.^I

^ILaboratório de Imunopatologia Keizo Asami and Departamento de Bioquímica, Universidade Federal de Pernambuco, Recife, PE, Brasil

^IIDepartment of Parasitology, School of Medicine, Chiba University, Japan

^{Correspondence} Correspondence to Luiz B. Carvalho Jr Laboratório de Imunopatologia Keizo Asami, Universidade Federal de Pernambuco, Cidade Universitária 50670-420 Recife, PE, Brasil E-mail: lbcj@hotlink.com.br

SUMMARY

A serological survey of Toxoplasma gondii infection in blood donors was carried out in order to identify seroprevalence in Recife, Brazil. Sera from 160 individuals (119 male and 41 female) were evaluated by using a Toxoplasma IgG-antibody enzyme immunoassay (Denka Seiken Co., LTD., Tokyo, Japan). The seropositive percentual for males (79.0%) showed to be higher (p < 0.05) than for females (63.4%). This percentage increases with age, ranging from 18.2% to 92.6% for individuals aging under 20 and 40-50 years old, respectively. For women of childbearing age (18-40 years) it was found a prevalence of 51.6%.

Keywords: Toxoplasmosis; Seroepidemiology; Human; Recife, Brazil.

RESUMO

Estudo epidemiológico de infecção por Toxoplasma gondii em doadores de sangue foi realizado com vistas ao estabelecimento da soroprevalência em Recife. Soro de 160 indivíduos (119 masculinos e 41 femininos) foram analisados mediante o emprego de ensaio imunoenzimático para a detecção de anticorpos IgG anti-Toxoplasma (Denka Seiken Co., LTD., Tokyo, Japan). O percentual de soropositivos para os indivíduos do sexo masculino (79,0%) foi maior (p < 0,005) do que para os do feminino (63,4%). Esta soropositividade aumentou com a idade, variando de 18,2% para os indivíduos menores de 20 anos até 92,6% para aqueles entre 40 e 50 anos de idade. Para as mulheres na idade fértil (18-40 anos) foi encontrada prevalência de 51,6%.

Toxoplasmosis is a disease caused by the ubiquitous protozoan parasite Toxoplasma gondii⁵. Most T. gondii infections among humans occur by ingestion of tissue cysts from infected meat or oocysts from soil, or by congenital transmission through the placenta^3,10. According to NETO et al.¹⁴, Brazil presents the highest prevalence of congenital toxoplasmosis reported so far. Blood samples (140,914) from all over the country were tested for IgM-class antibodies and 47 cases confirmed. This finding suggests a prevalence of 1 per 3,000 births.

Although toxoplasmosis is a worldwide dispersed infection, seropositivity levels vary widely among different regions of the globe⁷. The prevalence rates change according to socio-cultural habits, geographic factors, climate and transmission route, and typically rise with age^4,7. In Brazil, prevalence studies have been carried out, mainly in the Amazon and southeast regions during the 70-80's. Seroprevalence ranged from 40-80%, with increasing levels according to age, low socioeconomic status, rural dwelling and raw meat cooking practices¹⁶.

Serological surveys indicate that about 80% of all primary infections are asymptomatic, due to the immune system effectiveness, but variable levels of the disease can affect immunocompromised individuals⁴. The epidemic of Acquired Immune Deficiency Syndrome (AIDS) has created an expanding population of susceptible individuals. Usually, people suffering from both AIDS and toxoplasmosis have been exposed to the Toxoplasma parasite earlier in life and the HIV infection simply allowed the Toxoplasma parasite to grow unchecked. The concomitant occurrences should be considered by public health policies especially in those countries with high toxoplasmosis prevalence where AIDS is concurrent with economic and public health problems¹⁵.

GUIMARÃES⁹ estimated the annual incidence of reported AIDS-associated opportunistic infections among AIDS cases at the national level in Brazil from 1980 through May 1999. The overall cumulative incidence rates/100 reported AIDS cases were: candidiasis - 59, tuberculosis - 26, Pneumocystis carinii pneumonia - 23, neuro-toxoplasmosis - 15, Kaposi sarcoma - 5, cryptococcal meningitis - 4 and protozoa infections - 4.

In 2000, Recife occupied the 11^th position in number of AIDS cases reported (211) and 56^th in number of cases/100,000 inhabitants (22,8) among Brazilian cities¹³, whereas the whole country presented a total of 15,012 cases and 9,0 cases/100,000 inhabitants in the same year.

The association of toxoplasmosis versus AIDS and the position of Recife in AIDS cases in Brazil was a strong reason to investigate the prevalence of IgG antibodies specific to Toxoplasma gondii in blood donors in Recife. These individuals usually living in the urban area are representative of those at risk from HIV/AIDS infection.

A solid phase enzyme immunoassay (EIA) for qualitative IgG detection was used in this study (Toxoplasma IgG-EIA™, Denka Seiken Co., LTD., Tokyo, Japan)¹¹. The instructions provided by the manufacturer were strictly followed. The optical density (a) established for each serum was divided by the mean value (b equal to 0.149) of a standard triplicate. Values of a/b > 1.0 were considered positive. Statistical analyses were performed using Origin® software, version 6.0.

Sera from blood donors were kindly provided by HEMOPE (Fundação de Hematologia e Hemoterapia de Pernambuco), a Brazilian reference center in hematology and hemotherapy, localized in the State of Pernambuco. The group consisted of 160 donors living in the urban area (Recife) of which 119 (74.4%) were men and 41 (25.6%) women, with ages ranging from 18 to 56 years.

Prevalence of 75% (n = 120) was found among the total number of donors. This result is within the range of general seropositivity expected for Brazil (40-80%), as indicated by REY & RAMALHO¹⁶. Other studies in different Brazilian municipalities, using various laboratory methods and sometimes targeting specific populations, also show comparable results^4,7,16,17.

Table 1 shows the prevalence of IgG antibodies specific to Toxoplasma gondii according to the sex of the blood donors. Usually it is not possible to detect a significant difference on the incidence of toxoplasmosis between sexes^2,7,10, but there are also studies pointing either to higher incidence for males^6,12 or for females^1,8. Our results showed a seropositive percentual for males (79.0%) somewhat higher (p < 0.05) than for females (63.4%).

The distribution of toxoplasmosis seroprevalence according to age ranges is presented on Table 2. As suggested by other authors^2,7,10,16,17, this percentage increases with age, reaching 90% for individuals over 40 years old.

For women of chiildbearing age (18-40 years) we found a prevalence of 51.6%. This result is comparable to that published by GARCIA et al.⁷, who found a seroprevalence of 70% for women of 16-40 years from the municipality of Jaguapitã, Paraná, Brazil. This could indicate that about half the women at childbearing age in Recife is/was infected and might be immunized against toxoplasmosis, reducing the risk of congenital infection.

ACKNOWLEDGMENTS

This work was financially supported by CNPq/CTPETRO (grant number 463655/001) and JICA. Authors are thanked to Dr. Paula Loureiro from HEMOPE for the sera of blood donors.

Received: 21 February 2002

Accepted: 08 August 2003

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