Saturday, February 18, 2012

Snakes Bite Dangerous In Africa

Despite urbanization and destruction of their habitat, venomous snakes remain plentiful in most parts of Africa. Throughout the continent, snakes are feared and misunderstood even though most are harmless. Venomous snakes bite humans only when they feel threatened, are trodden on or picked up inadvertently. Snakes are creatures that inspire awe, reverence and even worship in some areas, and they are exhibited as performing animals by traditional snake charmers. Despite this, they are usually loathed and killed on sight. Their survival depends on their remaining undetected. Snakes co-exist with humans in homes, gardens and outhouses but their presence usually goes unnoticed.

Fear of snakes is understandable since they are responsible for an untold number of bites and numerous deaths as well as cases of permanent physical handicap. No country is free from the risk of snakebite, and in some rural areas, such as the Benue Valley of northern Nigeria, snakebite is a leading cause of morbidity and mortality among farmers, pastoralists, hunters and children. Snakes such as puff adders (Bitis arietans) also kill and injure many domestic dogs and grazing animals.

The exact burden of human suffering attributable to snakebite is difficult to determine because bites occur most commonly in rural areas where the first impulse of many bite victims is to seek the help of a trusted traditional healer rather than go to a Western-style hospital where their attendance may be recorded and reported to a national authority. The inadequacy of official snakebite statistics is well illustrated by Swaroop and Grab’s survey of global snakebite mortality (Swaroop and Grab, 1954). During a sixyear period 1947–52, an annual average of 27.7 snakebites with 1.5 deaths per 100 000 population was reported in the whole of the northern region of Nigeria. However, in the six-year period 1964–69, an annual average of 158.8 bites with 8.3 deaths per 100 000 population was reported from one district (Muri) with a population of some 250 000 people (Warrell and Arnett, 1976). Some epidemiological data on snakebite in African countries are presented in Chapter 3 but the figures are likely to underestimate the true magnitude of the problem.

A possible way to obtain reliable figures is by completing questionnaires in randomly selected households as part of a properly designed community-based study. Only a few such studies have been published from Africa. In Bandafassi, Senegal; Muri Division, Nigeria adult snakebite fatalities per 100 000 population per year, respectively, were reported. These studies revealed an unexpectedly high rate of snakebite mortality and confirmed the low rate of hospital attendance (8.5% in Malumfashi, 27% in Kilifi), the preference for traditional treatments (36% of Kilifi patients visited the traditional therapist) and high incidence of persisting symptoms among survivors (19% in Malumfashi, 36% in Kilifi) including some amputations and deformities. Snakebite is an important public health problem in these areas and deserves far more attention from health ministries and other authorities.

African populations are not equally affected by snakebite. Children account for 20%–40% of cases in most published studies. Farmers and other agricultural workers are the most common victims. The occupational aspect of snakebite must be better appreciated as the targeted workers, which include farmers, plantation workers, herdsmen and hunters, are prime food producers and therefore particularly valuable members of the community. Although snakes are almost universally feared and even hated, their essential role in the balance of nature must not be forgotten. They protect crops and food stores by preying on large numbers of rodents. Without this control, bourgeoning numbers of rodents might cause epidemics of plague, typhus, leptospirosis, Lassa fever and other potentially lethal diseases that are transmitted from rodents to humans.

Larger snakes such as pythons and Bitis species are frequently eaten as delicacies and valuable protein supplements, and also as part of various ju-ju rituals in West Africa. Humans can become infected with Armillifer armillatus (pentastomid), a parasite of the respiratory tract of snakes, by eating uncooked snakes. Calcified nymphs of this pentastomid were found in 1.4% of abdominal radiographs in Ibadan, Nigeria and in 22.5% of autopsies in Democratic Republic of Congo, 8% in Cameroon and 5% in West Africa (Palmer and Reeder, 2001). These observations show how commonly snakes are eaten in Africa.

Goats, sheep, domestic fowl and pets should be protected from pythons, but these snakes are valuable in controlling the numbers of feral cats and dogs. Elimination or eradication of snakes, even if it were possible, is therefore undesirable. Snake predators such as storks, hornbills, small carnivorous mammals and monitor lizards control their numbers. It is clear that, despite the very real risk of snakebite, humans must learn to co-exist peacefully with snakes, respecting their place in nature while minimizing the danger they pose by avoiding them as far as possible.


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