10.2.4.3. Meningitis
Major epidemics of meningococcal infections usually occur every 5-10 years
within the African "meningitis belt;" they usually start in the middle
of the dry season and end a few months later with the onset of the rains (Greenwood,
1984). Between February and April 1996, the disease affected thousands of people
in parts of northern Nigeria, many of whom died (Angyo and Okpeh, 1997). This
epidemic spread from the original meningitis belt to Kenya, Uganda, Rwanda,
Zambia, and Tanzania (Hart and Cuevas, 1997). One of the environmental factors
that predisposes to infection and epidemics is low humidity (Tikhomirov et
al., 1997). However, a climate-meningitis association was not clear in parts
of the Gulf of Guinea (Besancenot et al., 1997). That this disease has
been limited to the semi-arid areas of Africa suggests that its transmission
could be affected by warming and reduced precipitation.
10.2.4.4. Rift Valley Fever
From 1931 (when the disease was first described) until the end of the 1970s,
Rift Valley fever (RVF) was considered to be a relatively benign zoonoses for
humans that periodically developed in domestic animals (especially sheep) following
heavy rains (Lefevre, 1997). Recent research indicates that although epizootics
in east Africa are associated with an increase in rainfall, a similar association
is unknown in west Africa (Zeller et al., 1997). Recent data from west
Africa indicate that the risk of a new epizootic is increasing in the region
(Fontenille et al., 1995), with significant exposure to the virus among
livestock herders and wildlife rangers during the wet season (Olaleye et
al., 1996). Following the 1997-1998 El Niño event in east Africa,
an RVF outbreak in Somalia and northern Kenya killed as much as 80% of the livestock
and affected their owners (WHO, 1998b). Many cases also were reported in Tanzania.
In Mauritania, the human epidemic was linked to the epizootic disease (Jouan
et al., 1989). Extensive research on mosquito vectors of RVF in Kenya
(mainly Aedes and Culex spp.) has clearly linked the risk of outbreak
with flooding (Linthicum et al., 1990). It can be expected that increased
precipitation as a consequence of climate change could increase the risk of
infections in livestock and people. Such new risks could cause major economic
and health problems for herding communities in Africa.
10.2.4.5. Plague
Plague is a flea-borne disease with rodents as reservoirs. The population of
rodents can increase suddenly following heavy rains as a result of abundance
of food (e.g., grain). During drought, rodents may migrate into human dwellings
in search of food. Development of fleas and the pathogens they carry can be
accelerated by increased temperature. Plague outbreaks recently have been reported
in Mozambique, Namibia, Malawi, Zambia, and Uganda (see WHO Outbreak Web site:
<www.who.int/disease-outbreak-news>).
10.2.4.6. Water-Associated Protozoal Diseases
Pollution of streams, wells, and other sources of rural water supplies by flooding
could introduce parasites such as giardia, amoeba, and cryptosporidium into
drinking water (Alterholf et al., 1998). These parasites assume a new
significance in HIV-infected individuals because of the latter's immunocompromised
status (Mwachari et al., 1998). Extreme weather events such as El Niño
have been associated with increased episodes of diarrhea.
10.2.4.7. Other Major Parasitic Infections
Shifts in the epidemiology of schistosomiasis, onchocerciasis, and filariasis
may take longer to become evident because these parasites are less sensitive
to the effects of climate than diseases such as malaria. Changes in the impacts
of climate on human trypnosomiasis may require substantial and permanent changes
in tsetse fly ecology. Little or no data are available on this subject.
10.2.4.8. Air Pollution-Associated Diseases
Biomass burning and massive importation of badly maintained vehicles could
result in increased air pollution—which, combined with increasing temperature,
would exacerbate health risks such as respiratory problems and eye and skin
infections (Boko, 1988).
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