Tanzanian study confirms that parasitic coinfection is commonplace

25 May 2010

Paul Chinnock

Source: Parasites & Vectors (see original article or PDF)

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Citation: Mazigo HD, Waihenya R, Lwambo NJ, Mnyone LL, Mahande AM, Seni J, Zinga M, Kapesa A, Kweka EJ, Mshana SE, Heukelbach J, Mkoji GM (2010). Co-infections with Plasmodium falciparum, Schistosoma mansoni and intestinal helminths among schoolchildren in endemic areas of northwestern Tanzania. Parasit Vectors; 3 (1):44.

An important issue when considering the infectious diseases of poverty is that people in the world’s poorest countries are at high risk, not just of one serious infection but of many. The great majority of research studies nevertheless each focus on a single disease. It is always of interest when researchers look at the prevalence of several infections in a community and record how many individuals in the community are afflicted with two or more coinfections.

A study in Tanzania has investigated the prevalence of three of the most important parasitic infections – malaria, intestinal schistosomiasis and soil-transmitted helminth infections – in 400 schoolchildren (aged 8–16 years) living in villages close to Lake Victoria.

The researchers employed a cross-sectional study design. They selected four schools at random and then, using a random numbers table, selected 100 children in each school who were tested for the presence of the parasites. Any child found to be infected was given appropriate treatment.

Over half of the children (54.5%) were found to be infected with a single parasite species and 29% were infected with two or more, including 2.8% who were triple infected. Only 16.5% had no infection.

The most common parasitic infection in these children was schistosomiasis; 64.3% tested positive for Schistosoma mansoni. The prevalence of Plasmodium falciparum malaria was 13.5%. The only soil-transmitted helminth found was hookworm but the prevalence of this parasite was also high – 38%.

The coinfection that was most frequently found was schistosomiasis and hookworm, accounting for 69% of coinfected children. The prevalence of S. mansoni–P. falciparum co-infection was 22.6%.

As research in several other locations has also found, schistosomiasis was most common in the under-13 age group, whereas the highest prevalence of hookworm was in children above that age.

There are few surprises in the findings from this study, though the authors note that schistosomiasis was more prevalent than has been the case in other surveys conducted in this region.

Nevertheless, the research provides a reminder of the need for integrated health care; vertical programmes, each focusing on one infection, are of limited effectiveness in addressing the needs of children who face many different challenges to their health. In their discussion, the authors stress the need to know more about the clinical consequences for those children who are coinfected. They refer to research [1,2] that suggests that children with multiple parasitic infections tend to experience more severe health problems than those with only one infection.

The authors remind us of the role of poor sanitation in increasing the risk of helminth infection and they argue that, “Although malaria and helminths have distinct means of transmission patterns, a variety of environmental and host factors may influence their epidemiological and geographical patterns of infections and diseases”. The underlying root cause of these parasitic infections is, of course, poverty.

References

1. Jardiam-Batelho A, Raff S, de Avilla Rodrigues R, Hoffman HJ, Diemert DJ, Correa-Oliveira R, Bethony JM, Gazzinelli MF (2008). Hookworm, Ascaris lumbricoides infections and polyparasitism associated with poor cognitive performance in Brazilian schoolchildren. Trop Med Int Health;13(8)994-1004. Available from: http://www.ncbi.nlm.nih.gov/pubmed/18627581

2. Sakti H, Nokes C, Hertanto WS, Hendratno S, Hall A, Bundy DAP, Satoto (1999). Evidence for an association between hookworm infection and cognitive function in Indonesian school children. Trop Med Int Health; 4(5):322-334. Available from: http://www.ncbi.nlm.nih.gov/pubmed/10402967

2010 Mazigo et al., licensee BioMed Central Ltd.

Source

Title:
Co-infections with Plasmodium falciparum, Schistosoma mansoni and intestinal helminths among schoolchildren in endemic areas of northwestern Tanzania.

Authors:
Mazigo HD, Waihenya R, Lwambo NJ, Mnyone LL, Mahande AM, Seni J, Zinga M, Kapesa A, Kweka EJ, Mshana SE, Heukelbach J, Mkoji GM

References:
Parasit Vectors 2010: Vol. 3, pp. 44

Abstract:
Malaria, schistosomiasis and intestinal helminth infections are causes of high morbidity in most tropical parts of the world. Even though these infections often co-exist, most studies focus on individual diseases. In the present study, we investigated the prevalence of Plasmodium falciparum-malaria, intestinal schistosomiasis, soil-transmitted helminth infections, and the respective co-infections, among schoolchildren in northwest Tanzania.A cross sectional study was conducted among schoolchildren living in villages located close to the shores of Lake Victoria. The Kato Katz technique was employed to screen faecal samples for S. mansoni and soil-transmitted helminth eggs. Giemsa stained thick and thin blood smears were analysed for the presence of malaria parasites.Of the 400 children included in the study, 218 (54.5%) were infected with a single parasite species, 116 (29%) with two or more species, and 66 (16.5%) had no infection. The prevalences of P. falciparum and S. mansoni were 13.5% (95% CI, 10.2-16.8), and 64.3% (95% CI, 59.6-68.9) respectively. Prevalence of hookworm infection was 38% (95% CI, 33.2-42.8). A. lumbricoides and T. trichiura were not detected. Of the children 26.5% (95% CI, 21.9-30.6) that harbored two parasite species, combination of S. mansoni and hookworm co-infections was the most common (69%). Prevalence of S. mansoni - P. falciparum co-infections was 22.6% (95%CI, 15.3-31.3) and that of hookworm - P. falciparum co-infections 5.7% (95%CI, 2.6-12.8). Prevalence of co-infection of P. falciparum, S. mansoni and hookworm was 2.8% (95%CI, 1.15-4.4).Multiple parasitic infections are common among schoolchildren in rural northwest Tanzania. These findings can be used for the design and implementation of sound intervention strategies to mitigate morbidity and co-morbidity.

PMID: 20482866
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