Del importe del valor nominal de los títulos de

Hookworm is endemic throughout the developing world. There are an estimated 900 million cases of infection (WHO, 1987b) and 60,000 deaths annually in Africa, Asia, and Latin America (WORLD HEALTH, 1984). These figures emphasize the public health importance of hookworm infection as a cause of morbid­

ity and mortality. The infection is a good indicator of life in squalid conditions, where the prevalence is sometimes as high as 80%. There is no direct evidence that man develops protective immunity to hookworm infection, but epidemiological studies suggest that some degree of immunity probably develops w i t h time (WHO, 1987b). Hookworm infection causes chronic blood loss and depletion of the body's iron stores, and must be considered an important factor in the etiology of tropical iron-deficiency anaemia, and this has implications for young children, pregnant women, and the health and productivity of adults whose livelihood and contribution to the economy depend on hard physical work (WARREN and MAHMOUD, 1984). The contri­ bution of hookworm infection to malnutrition is in general not as well established as its role in iron-deficiency anaemia (WHO,1987b). Lack of sanitation, indiscriminate defecation, and high egg production ensure constant exposure to infection, as do the practices of using the same places for defecation and going barefoot.

LACAZ et al. (1972) studied the relationship between basic sanitary conditions, socioeconomic status and hookworm infection in Sâo Paulo, Brazil, where 6,835 school pupils were examined and grouped according to the availability of sanitary services. Those living in marginal urban areas without domestic running water and sewerage facilities and those from rural areas living in bad conditions showed hookworm infection much more frequent than those living in urban areas with sanitary services and belonging to comparatively well-off families.

ARFAA et al. (1977) found in Iran that villages which received sanitation improvements had a 4% decrease in hookworm preva­ lence, and a 26% reduction in egg count among those infected. These prevalence and egg count reduction values for the group receiving sanitation and chemotherapy were 69% and 88% respectively, for the chemotherapy only group 73% and 87%, and for the control group, 11% and 12%. The results are confounded because each cohort began with a different hookworm preva­

lence. The sanitation-only cohort started with 71% infected, while the control group began with 44%. The way in which

interventions were assigned to the villages was not stated.

KILLEWO et al. (1991) studying the pattern of hookworm in a periurban area in Dar es Salaam, found from the lack of clustering by household that most of the transmission of this parasite in the study area was between households rather than within them, and that the household, and the latrine in parti­

cular, was not the primary focus of transmission in the area.

In their review of eleven studies relating hookworm infection to excreta disposal facilities with or without water supplies ESREY et al. (1990) found five studies reporting positive findings: two involving water supply and sanitation (CHANDLER, 1954; SCHLIESSMANN et al., 1958) and three involving sanita­ tion only (CORT et al., 1929; SWEET et al., 1929; KHALIL, 1931).

2.4.3.3. Trichuriasis

Trichuriasis is an important worldwide disease, predominantly of children (COOPER and BUNDY, 1988). Considering its worldwide distribution and high prevalence, trichuriasis has been neglected more than most other intestinal parasitic diseases (WARREN and MAHMOUD, 1984). The degree of morbidity

is related to the intensity of the infection.

Chronic impairment of the host's nutritional status should be suspected when diarrhoea, hypoalbuminaemia, and iron-defi­ ciency anaemia are observed in association with the presence of the parasite (WHO, 1987b). Children with intense infections

of

Trichuris trichiura

with any chronic colitis (COOPER, 1991). The severe suppression of height growth of such children (COOPER et al., 1990) and the adverse effect on certain cognitive functions in children with moderate to heavy infections has recently been

shown in Jamaica (NOKES et

al

High prevalence of

Trichuris trlchiura

al,,

1988; FORRESTER et

al.

al.,

Despite the importance of sanitation as a barrier to the transmission of

Trichuris trichiura

al.,

1 9 8 3 b ) .

HENRY (1981) showed with data from Saint Lucia that the preva­ lence of infection with

Trichuris trichiura

Trichuris trichiura

without sanitation and an urban area with sanitation in Kampala was almost equal, while the findings of the study of FEACHEM et

al.

Trichuris trichiura,

In summary, in this chapter was presented that: several diseases are related to inadequate sanitation; the impact of improved sanitation on child health has been studied, although few studies have been conducted in urban areas; some methodo­ logical pitfalls were identified in such studies; sanitation has also been reported to produce a differential health impact depending on the presence or absence of other risk factors; diarrhoea incidence, mortality, prevalence of intestinal helminth infections and, more recently, nutritional status h a v e been utilized as health indicators to evaluate the impact of improved sanitation; difference between neighbourhoods in environmental conditions may be associated with larger differentials in health than differences in household-level facilities (KOOPMAN et

al,

a l

CHAPTER 3