In Her Lifetime Female Morbidity and Mortality in Sub-Saharan Africa (1996) / Chapter Skim
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10 Tropical Infectious Diseases
10 Tropical Infectious Diseases
Pages 200-241
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Table 10-2 presents the burden of disease measured in DALYs for SubSaharan Africa by sex and age. Of the tropical infectious diseases discussed in this chapter, five are life-threatening: malaria, schistosomiasis, 200
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Table 10-6, which presents a detailed analysis of the sequelae of the tropical infectious diseases across the female life span, makes it abundantly clear that such a narrow focus does not fit the facts. The third perspective is that, with the exception of the role of the reproductive factor, any other differences in male/female mortality and disability rates are caused by variations in the nature and degree of exposure and in the social.
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MALARIA Malaria remains the most important and widespread of the tropical diseases, and levels of malaria transmission are higher in Sub-Saharan Africa than anywhere in the world (Bradley, 1991~. The region accounts for over 80 percent of the 110 million clinical cases worldwide each year, 90 percent of the estimated 275 million people in the world who are infected carriers of the parasite, and most of the estimated one to two million deaths that malaria causes annually (Najera et al., 1993; WHO/TDR, 1991a)
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Very few malaria studies present data disaggregated by gender, and this has certainly not been done in any extensive or reliable way. This is largely true for all the tropical diseases, and results from the lack of sensitivity to the possibility of gender-specific differences in disease outcomes mentioned above (Vlassoff and Bonilla, 1994)
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Recrudescence of preexisting malarial infection, placental infection, and frequency of low birthweight infants are all more common in primigravidae than in multigravidae (Hendrickse, 1987) , and rates of low birthweights brought about by malaria among primigravidae are particularly high, ranging from 9 to 40 percent (Brabin, 1985; see Tables 10-7 and 10-8~.
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and a recent set of hospital and community studies in central Sudan by Taha, Gray, and colleagues (Taha et al., 1993) found significant associations between a maternal history of malaria and low birthweight, a higher risk of low birthweight among primiparous women compared with multiparous
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Brabin (1991) has observed seasonal variations in parasite rates in pregnant women, citing six studies from four African countries that reported higher parasite rates in the wet season than in the dry season (see Table 10- 109.
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intercalatum, in Central and West Africa (Warren et al., 1993~. Schistosomal infection and the patterns of its transmission in endemic communities are powerfully influenced by ecolo~ical factors.
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The epidemiology and morbidity of schistosomal infection depend on several factors: timing and duration of water contact and exposure, penetration of cercariae, and nutritional status. Of these, it is water contact that heads the list of human activities that determine the intensity of schistosomal infection (Jordan, 1972; Ol~afor, 1990; Warren, 1973~.
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Other studies in Ethiopia also reported increased susceptibility in young boys, adolescent girls, and women ages 15 to 34, and found a clear correlation with the amount of water contact (Hiatt, 1976; Polderman, 1974~. Nonetheless, later studies in Mali and The Gambia found that infection rates in males and females were similar, despite apparent differences in exposure patterns (Brinkmann, et al., 1988; Wilkins et al., 1984~.
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concluded that while examination for hematuria is a reliable and sensitive morbidity indicator, egg count reliability is questionable because of the high day-to-day variability in egg excretion. The most significant morbidity effects from schistosomal infection are urinary tract sequelae, including calcification in the lower tract, vesico-ureteric reflux, and hydronephrosis from S
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. As in the case of so many tropical infectious diseases, exposure to the infective vectors of African trypanosomiasis is closely related to individual and community behavior, notably the work patterns of males and females and the different age groups (Robertson, 19639.
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In a recent review, Brabin and Brabin ~ 1992) suggest that the observed sex differences in these cohorts are attributable either to increased susceptibility to disease in women of reproductive age or to loss of asymptomatic status during pregnancy.
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Because at least some males are absent, as noted above, this theory is open to question. African Trypanosomiasis and Pregnancy Like malaria, African trypanosomiasis has special impact on women during pregnancy.
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Although the disease is not fatal, it generates a huge burden of disability and ranks fourth among all the tropical infectious diseases included in the GBD calculations. The total burden of DALYs from trachoma in Sub-Saharan Africa for both sexes of all ages was 901,000 in 1990; still, that burden is half the 1.8 million DALY burden produced by the third-ranked disease, African trypanosomiasis.
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In addition, the pattern of transmission for the disease is such that adult females who care for young children in domestic environments are at distinctively high risk. A meticulous study in Tanzania provides evidence that close physical contact with preschool children, especially preschool children with trachoma, is associated with an increased odds ratio for active trachoma in women and may also be associated with development of chronic sequelae (Congdon et al., 19933.
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Dracunculiasis in Children and Adolescents The picture of age and sex differences in Guinea worm infection, like every other tropical disease, is spotty. Information about the disease in infancy is slight, except for published epidemiologic surveys that show dracunculiasis infection to be rare in the first year of life.
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Dracunculiasis in Adult Females The highest rates of Guinea worm infection occur in adults between ages 15 and 45 (Belcher et al., 1975~. In an exhaustive review, Muller (1971)
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reported bleeding during pregnancy caused by retroplacental worm location, as well as a pattern of repeated spontaneous abortions of uncertain etiology in a very short time period, a pattern terminated successfully by worm removal. The debilitation produced by Guinea worm infection makes itself felt across much of the female life span.
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The simple, economical procedure of filtering drinking water through a cloth to remove the crustacean intermediate host seems to be a culturally acceptable and effective control intervention in many endemic areas, and is the method of choice for controlling this helminthiasis until enclosed water supplies are available. Provision of such supplies, combined with health education, has been shown to eradicate the disease within three years (Edungbola et al., 1988; Edungbola and Watts, 19903.
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Infection with W bancrofti leads to the most severe form of lymphatic filariasis, affecting breasts, genitalia, and all limbs; it can also induce tropical pulmonary eosinophilia.
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Yet the Taraba River Valley study cited above reported that all forms of visual impairment increased with age in a similar fashion for both males and females, and in a study in the Onchocerciasis Control Programme area, the only significant differences in ocular lesions were found in individuals with lesions of the posterior segment of the eye, a condition more typical of male symptomatology (Remme et al., 1989~. Given the present state of knowledge, the hypothesis must be that any gender-specific differences in symptomatology and microfilarial densities derive from differences in exposure rather than from any inherent sex differences (Brabin, 1990~.
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Onchocerciasis in Adult Females The skin lesions produced by O volvulus may begin as early as age 5, and continue to be produced into adulthood; after age 40, the number of exposed persons with different forms of onchocercal lesions is significantly higher than those who will eventually become blind.
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The study provides no further information on blindness in women or its impact on them, nor does any other that the authors of this chapter have been able to identify. LEISHMANIASIS AND LEPROSY Four of the six major tropical diseases that produce visible disfigurement have already been discussed in this chapter: schistosomiasis, dracunculiasis, onchocerciasis, and lymphatic filariasis.
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. Leishmaniasis ranks sixth in DALY burden in Sub-Saharan Africa, following not far behind onchocerciasis.
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CONCLUSIONS It is clear that the tropical infectious diseases are closely associated with deprivation: with poverty; isolation, and powerlessness; with lack of clean water, sanitation, and effective vector control; and with unavailability of adequate preventive and curative medical response. It is also clear that vulnerability to infection is closely associated with exposure and, in turn, the socioeconomic and cultural factors that shape the timing, duration, and intensity of that exposure.
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While it is certain that differential exposure is a dominant factor in infection, there are tantalizing clues in research on nonparasitic infections that there may be genetic and sex-specific differences in response to infection that may not be linked to reproductive function per se. Such findings as the sex differences in the incidence of uropathy and hematuria in children between birth and age 4 are provocative; their meaning and the possibility of other such differences in additional tropical infectious diseases are unknown and could be relevant to understanding of those diseases.
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If there is no reason to think this is the case, then it would perhaps be a misguided investment of increasingly scarce funds for biomedical research, but the question should at least be raised. · Work in parasitic diseases, notably malaria, schistosomiasis, and dracunculiasis, reflects differences between Western biomedical and indigenous concepts in perceptions of the meaning and management of the tropical infectious diseases.
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Paper presented at the WHO/TDR Meeting on Women and Tropical Diseases, Oslo, April 1992. Anyangwe, S., O
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1990. Sex differentials in susceptibility to lymphatic filariasis and implications for maternal child immunity.
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1989. Human African trypanosomiasis: sleeping sickness: new endemic foci in Bendel State.
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and malaria. In Women and Tropical Diseases, P
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Paper presented at the WHO/TDR Meeting on Women in Tropical Diseases, Oslo, April 1992. Polderman, A
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1994. Gender-related differences in the impact of tropical diseases on women: what do we know?
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WHO/TDR (World Health Organization, Special Programme for Research and Training in Tropical Diseases)
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