Curtis Abraham
14 August 2008
analysis
Nairobi — Last year's outbreaks of the deadly Marburg and Ebola Hemorrhagic Fever viruses in southwestern Uganda and in the neighboring Democratic Republic of Congo's province of Kasai Occidental and the sporadic outbreaks of Avian Influenza (Bird Flu) across the continent once again bring to light the threat zoonotic diseases pose to sub-Saharan Africa in particular and the world generally.
According to recent analysis more than 60 per cent of the estimated 1,415 infectious diseases known to modern medicine are capable of infecting both animals and humans. Most of these diseases such as anthrax, Rift Valley fever and monkey pox are zoonotic, meaning they originated in animals but have crossed the species barrier to infect people.
It is estimated that about 75 per cent of the new diseases that have affected humans over the past 10 years have been caused by pathogens (infective agents) originating from animals or animal products. This was the case of the HIV-- the virus that causes Aids, which experts believe jumped the Darwinian divide from apes to humans.
Such diseases are of course not confined to the developing world. In 2003 there was an outbreak of human monkey-pox in the American states of Illinois, Indiana and Wisconsin. Human monkey-pox is a rare zoonotic viral disease that occurs primarily in equatorial West and central Africa.
The outbreak in America occurred when a Wisconsin prairie-dog dealer allowed several of his animals to mix with rodents recently imported from Ghana that happened to be carrying the Monkey-pox virus. Luckily, no one died despite there being 71 reported cases of the disease in six mid-western states.
And it isn't only humans who are at risk of disease. Domestic animals, as the bird flu (H5N10) or Avian Influenza outbreaks in Asia, Europe and Africa have proven, are equally vulnerable to infectious ailments.
Livestock agriculture is the most important industry across sub-Saharan Africa, and disease is its biggest enemy. Overall, the industry represents 25 per cent of the gross domestic product (GDP) of the region, and, in certain countries, provides enough stock for export.
However, compared with other parts of the world, Sub-Saharan Africa has the heaviest burden of animal diseases. For example, 12 out of the 15 diseases that were considered by the Office Internationale des Epizooties as the most contagious are found in Africa.
According to experts, Africa is not threatened by a single malaise such as HIV and Aids or Avian Influenza but by a combination of various human, plant and animal diseases, which can have potentially devastating social, environmental and economic effects.
But why has there been a rise of new zoonotic diseases such as West Nile Fever, Rift Valley Fever, Marburg and the emergence of new virulent organisms when health care throughout the world is arguably the best it has ever been in the history of humanity?
The misuse of antibiotics by Sub-Saharan Africans is one key consideration. Patients in poor areas of the continent have poor prescriptions habits by not taking the full dosage of their prescribed medications. Furthermore, even if the patient in question is taking the proper dosages, many Africans are unable to afford the necessary full course antibiotic prescriptions. There is also the lack of government regulation of pharmacies many of which sell drugs without a physician's prescription.
Rapid population growth in sub-Saharan Africa is also another important factor. Along with population increase comes the need for more arable and grazing land and the exploration of new forest, swamp and cave habitats. This raises the likelihood of exposure to 'new' infectious agents in those environments, and could result in the emergence of new disease pathogens.
As population grows there is also an increase in the demand for food. In sub-Saharan Africa and elsewhere, people are more and more turning to wild animals for food. This high demand for bush meat in the countries of the Congo Basin is helping to fuel the increase in outbreaks of such illnesses as Ebola Hemorrhagic Fever. Ebola, like the HIV virus that causes Aids, passed into the human population through contact with blood from infected primates such as gorillas and chimpanzees as well as other primates like monkeys who regularly from part of the bush meat trade.
However, the multi-billion dollar bush meat industry is a key contributor to local economies throughout the developing world. It is also among the most immediate threats to tropical wildlife.
The consumption of bush meat is particularly acute across west and central Africa where there are still large equatorial forests. In fact, the Congo River Basin is home to one of the biggest expanse of tropical rainforest in the world. Cameroon, Central African Republic, Democratic Republic of Congo, Equatorial Guinea, Gabon and the Republic of Congo have a combined forest area of 1,856,207 kilometres squared -- one of the largest in the world. Add to this the estimated combined forest and urban population of the Congo Basin of 5432,945,932 who consume an astonishing 1,196,395,911 kilograms (one million to five million tones) of bush meat annually. You now appreciate why wildlife conservationist call it the Bush meat crisis.
These vast forest areas harbour various monkey and antelope species. But its Africa's highly endangered Great Apes: gorillas, chimpanzees and bonobos whose very existence is being severely affected by the bush meat trade.
Recent scientific surveys of great ape populations in Gabon, which has one of the largest populations, indicates that the numbers of gorillas and chimpanzees declined by more than half between 1983 and 2000. But it is not only the bush meat trade that has decimated the ape population of West and Central Africa. Ebola has killed tens of thousands of gorillas and chimpanzees.
But the bush meat trade in sub-Saharan Africa has also been linked to the decline of fish stocks in West Africa. According to experts people substitute wildlife for fish in ears of fish scarcity. In 2005 researchers found that declining fish stocks were fuelling a multibillion- dollar meat trade in West Africa.
In Ghana more than half of the country's 20 million people reside within 100 kilometres of the coast, where fish is the primary source of protein and income. However, using 30-year data collected monthly by rangers in six nature reserves in Ghana, researchers have found a direct link between fish supply and the demand for bush meat in Ghanaian villages.
Looking at data for the years 1970 to 1998, researchers found that in 14 local food markets, residents substituted bush meat as an alternative to fish and the number of poachers observed by rangers in parks increased when fish supply was limited or its price increased.
During the same period trawler surveys conducted in the Gulf of Guinea, off Ghana's coast, since 1970 along with other regional stock assessments, estimate that fish biomass in near-shore and off-shore waters has declined by at least 50 per cent.
In the same period, there has been a threefold increase in human population in the region. The researchers suspect the decline in the availability of fish at local Ghanaian markets is linked to heavy over-fishing in the Gulf of Guinea.
The Gulf of Guinea is one of the most over fished areas of the world. Declines in fish stocks in waters off West Africa have coincided with more than ten-fold increases in regional fish harvests by foreign and domestic fleets since 1950.
Shipping fleets subsided by the European Union (EU) have consistently had the largest foreign presence off West Africa, with EU fish harvests there increasing 20 times from 1950 to 2001.
As the outbreaks of zoonotic diseases increase, indigenous Africans (and others communities in developing countries) might hold the key to disease prevention and containment.
Some pioneers in the field of modern medical anthropology agree that the global fight against emerging zoonotic diseases as well as re-emerging contagious and infectious ailments in Sub-Saharan Africa and elsewhere has failed to incorporate traditional African medicine for disease control and prevention.
This negative attitude towards indigenous notions of contagious diseases stems largely from the assumption that African health beliefs are primarily based on witchcraft, sorcery or black magic. Experts have indeed found this to be true in the realm of mental illness in sub-Saharan Africa (perhaps due to a superficial likeness between possession by spirits and symptoms of some mental illnesses) but curiously not so when it comes to infectious diseases.
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