Alert As Virus Leaps Over Buffer Zone
The Nation (Nairobi)
NEWS
January 23, 2007
Posted to the web January 22, 2007
By Gatonye Gathura
Nairobi
The virus causing Rift Valley Fever has outmanoeuvred local and international experts, vaulting over a buffer between North Eastern and Coast provinces to land in Maragua, Central province, for the first time. This has created fear that the killer bug could be headed for Nairobi.
The buffer was created by the ministry of Livestock Development, with help from World Health Organisation (WHO) and Food and Agricultural Organisation (FAO).
It aimed at vaccinating two million animals while maintaining zero contact with livestock from other parts of the country.
Increase dramatically
The jump could see the number of animals to be vaccinated increasing dramatically, and possibly overwhelming available capacity.
Started about three weeks ago, the programme had vaccinated only 120,000 animals by Sunday. The country depends on erratic supply of vaccine from the United States and South Africa, although the virus was first isolated in Kenya and a cure developed by local scientists.
The Director of Veterinary Services, Dr Joseph Musaa, says Kenya should have strategic reserves of the vaccine "because the problem occurs here and is bound to recur."
Locally, the vaccine is developed at the Kenya Veterinary Vaccine Production Institute, Kabete, but the supplies cannot meet the current demand. "It is ironic that we have to import vaccines from countries that acquired the technology from us," he says.
The outbreak is the second most severe since 1930. But this time around, its re-appearance was predicted as early as September.
But the virus met little organised resistance and went ahead to claim over 100 human lives, scores of livestock and wildlife. It is feared the fever could spread to Juba valley in the Sudan, triggering a major food crisis in the region.
What happens next is also predictable, the bug will soon go into hiding -it is not clear where to - but it will come back in three to seven years.
The cycle will continue... unless two things happen: pre-emptive measures are made to mitigate human and animal loses, or mutation of the virus - changing genetically and becoming even more virulent. Climate factors could also make it alter its visiting and parasitic habits.
In September, a UN Food and Agricultural Organisation publication quoted the US National Aeronautics and Space Administration warning that rise in temperatures in the region could spark an outbreak of the disease.
By early November, local weathermen had correctly predicted floods and landslides in several parts of the country, including North Eastern province.
"It was too obvious not to see it coming. But no pre-emptive action was taken. We are famous for closing the barn door after the horse has bolted," said the director of Kenya Medical Research Institute (Kemri), Dr Davy Koech, last week.
He said there had been enough warning, but requirements such as animal vaccines and awareness programmes were brought in long after the virus had struck.
In candid discussions with top scientists from Kemri and US Centres for Diseases Control, it came out clearly that Africa has to rein in the bug as a joint and urgent concern.
The fever is geographically confined to Africa, except once in 2000 when an outbreak was reported in Saudi Arabia and, subsequently, in Yemen. The source was later traced to East Africa.
The fever is generally found in eastern and southern Africa, mainly among livestock keeping communities. The most notable outbreak in Kenya was in 1950-1951, which resulted in the death of an estimated 100,000 sheep.
Exported from Sudan
In 1977, the virus was detected in Egypt, but it was suspected to have been exported there through infected animals from Sudan.
It has once afflicted Senegal, in West Africa, following heavy floods.
The 1998 outbreak was the most severe in Kenya. It caused 400 human deaths.
Currently, there is no established course of treatment. But the drug ribavirin, an antiviral, has modest success.
The virus causes haemorrhagic fever - just like Marburg and Ebola do - but it is less virulent.
Fatalities from RVF, according to doctors, are low, possibly about 10 per cent of hospitalised cases and about one per cent of all infected persons. But with viruses, this could change dramatically, as happened with bird flu and HIV (human immuno-deficiency virus).
Luckily, there is no evidence that RVF virus has changed since it was first discovered in 1930 in Kenya, says Dr Kariuki Njenga of the Centres for Disease Prevention and Control in Nairobi.
Dr Njenga is overseeing diagnostic aspects of the current operations in Garissa and is also running ongoing research on the virus in Ijara.
"Something has me very worried, this time around," he said in an interview. "Ordinarily, the disease in livestock mainly manifests in mass abortions. But this time we are seeing the animals just dropping dead. It is very unusual."
Kemri principal investigator Rosemary Sang has collected 60,000 Aedes mosquitoes from the affected sites. With the help of US scientists, she is trying to determine what the country is dealing with now.
Aedes, Dr Sang explains, are a group of 24 species of mosquitos - the primary vector in transmitting RVF virus. "The virus engorges itself inside the eggs of mosquitoes before they are laid. The eggs are a reservoir for the virus. Once laid, they do not hatch until conditions are favourable and can stay put for even 10 years. Sustained flooding seems to trigger the eggs to hatch."
Once the mosquito bites an animal, specifically a herbivore, it infects it with the virus and the cycle begins.
Studies suggest that other types of mosquitos and insects can also spread the virus, so people are advised to sleep under bed nets.
Garissa is the epicentre of the current epidemic, and not for the first time. In the 1997-98 outbreak, 50 per cent of all human deaths were reported in Garissa. "We think there is a wildlife reservoir around this area which hosts the virus without affecting it," says Dr Njenga.
Just before the floods, he had a research team in Ijara. "We wanted to find out if there was a low-level incidence of the disease there. We were not able to conclusively determine this but early indications are that the virus is not active in non-epidemic periods."
He suspects that buffaloes, kudus and gazelles could be reservoirs of the virus. "Much research still needs to be done to get firm answers," he says.
It is this theory of a host wild animal that explains why the epidemic is in North Eastern, and not in Bundalangi where floods occur frequently.
Garissa, the scientist further explains, is the major urban centre of the region. It hosts a big livestock market that brings humans and animals to an unhealthy proximity.
Last week, Dr Njenga said Kemri was expecting suspect samples from Somalia for laboratory analysis. However, because of the security situation in the country, researchers say they are unable to get a clear picture.
The US Agency for International Development says that if the current animal vaccination programme fails, the fever could spread to the Sudan, which could adversely affect local and regional livestock export markets.
A sampling of those affected by the disease, just as in previous outbreaks, indicated that most of them were herdsmen, worked in abattoirs, or had constant contact with livestock and their products. This suggests that mosquitos and other insects are a lesser threat.
Reduce new infections
"But you must remember that mosquitos are the primary vector, transmitting the virus from one animal to the other. If the cycle is broken, we could reduce new infections."
Unlike malaria, which can be transmitted from one person to another by mosquitos, Dr Njenga says this mode of transmission is not major with RVR virus. "Research shows it stays in the human blood for a very short time, hence it is hardly available for the next insect to transmit it. This explains partially why the virus is not affecting whole families."
An effective vaccine for livestock exists, but none for humans. The logic for this is that animal vaccines are cheaper and easier to manufacture. Those for humans require heavy investments and strict protocols only afforded by big multinational drug companies, governments or WHO programmes.
Researchers say the Government and foreign agencies have responded well and that the situation could be arrested soon.
In the early stages, CDC transferred a high security laboratory unit from Nairobi to Garissa hospital, for which they are meeting diagnostics costs, while a special RVF ward in the hospital is funded by Medicines sans Frontiers. Other collaborators include WHO and several UN bodies.
Minimise any contact
The most important thing to do is to minimise contact between unclean livestock and humans, through what the veterinary department calls "ring" vaccination.
The ring, prepared by WHO and FAO, is a buffer between North Eastern, Eastern and Coast provinces, and the rest of the country.
Animals in this ring are vaccinated in a highly managed way. If veterinary officials find a particular herd has infected animals, they don't vaccinate it as this would be a waste. They move to the next herd.
However, both herds are sprayed with synthetic pyrethrin chemicals to ensure mosquitos don't bite the animals for the next two weeks.
Also, local communities are advised not to consume animal products - even of vaccinated herds. All this, says Dr Musaa, will be reviewed in February. Respective communities will then be advised accordingly.
