Cholera, Yellow fever, Ebola, Plague on the rise

Dec 06, 2009

EXPERTS have given the following list that includes pathogens or diseases that may spread as a result of changing temperatures and precipitation levels. However, the list is not comprehensive and subsequent studies may add other pathogens, says Dr. Issa M

By Vision Reporter

EXPERTS have given the following list that includes pathogens or diseases that may spread as a result of changing temperatures and precipitation levels. However, the list is not comprehensive and subsequent studies may add other pathogens, says Dr. Issa Makumbi, an epidemiologist at the Ministry of Health.

Cholera
Cholera is a water-borne diarrhoea disease affecting humans. It is caused by a bacterium, vibrio cholera, which survives in small organisms in contaminated water sources and may also be present in raw shellfish such as oysters.

Once contracted, cholera becomes deadly. It is highly weather dependent and increases if water temperature are directly correlated with the disease occurrence. Rising global temperatures due to climate change are expected to increase incidence of this disease.

Ebola and marburg
Ebola haemorrhagic fever virus and its closely related cousin, the Marburg virus, easily kill humans, gorillas and chimpanzees. Currently, there is no known cure for the disease.

There is significant evidence that outbreaks of both diseases are related to unusual variations in rainfall and dry season patterns. As climate change disrupts and exaggerates seasonal patterns, we may expect to see outbreaks of these deadly diseases in new locations and more frequently, says Dr. Makumbi.

Intestinal and external parasites
Parasites are widespread throughout terrestrial and aquatic environments. As temperatures and precipitation levels shift, the survival of parasites in the environment will increase in many places, infecting an increasing number of humans and animals.

The nematode, Baylisascaris Procyonis, is spread by the common raccoon and is deadly to many other species of wildlife and humans, says Dr. Joseph Senzoga, Kampala City Council’s district coordinator of epidemic outbreaks.
“Monitoring of parasites and loads in wildlife and livestock help us identify the transmission of these infections between domestic and wild animals,” he says.

Sleeping sickness
Also known as trypanosomiasis, this disease affects people and animals. It is caused by the Protozoan, Trypanosoma Brucei and transmitted by the tsetse fly. The disease is endemic in certain regions of Uganda, affecting 80,000 people annually and more than 10 deaths each year.

Cattle are a major source of the disease, but wildlife can also be infected and maintain the disease in an area. Direct and indirect effects (such as human land use patterns) of climate change on tsetse fly distributions could play a role in the distribution of this deadly disease.

Tuberculosis
According to Senzoga, tuberculosis is problematic in Uganda, affecting humans and wildlife like buffalos and lions. Humans can get the disease through consumption of unpasteurised milk. The human forms of tuberculosis can also infect wild animals.

“But climate change impacts on water availability due to drought are likely to increase the contact of wildlife and livestock at limited water sources, resulting in increased transmission of the disease between livestock and wildlife and livestock and humans,” he adds.

Yellow fever
Found in the tropical regions of Africa and parts of Central and South America, this virus is carried by mosquitoes. Although the disease has been eradicated from Uganda, Makumbi says, changes in temperatures and precipitation levels may cause it to reappear.

Plague
Although this is one of the oldest infectious diseases in Uganda, Senzoga says, it still causes significant deaths in wildlife, domestic animals and humans in certain parts of the country. “It is spread by rodents and their fleas.

Alterations in temperatures and rainfall are expected to change the distribution of rodent populations around the globe, which would lead to further spread of outbreaks,” he says.

Avian influenza
Avian Flu, Senzoga says, occurs naturally in wild birds, though often with no consequences. The virus is shed by infected birds via secretions and faeces. Poultry may contract the virus from other domestic or wild birds.

The disease also infects humans and has the potential to evolve into a strain that can spread from human to human.
“Although the movement of the disease from region to region is largely driven by the trade in poultry, changes in climate such as drought can disrupt the normal movement of wild birds, bringing both wild and domestic birds into contact at the remaining water sources. Humans may contract the disease,” Dr. Senzoga adds.

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