11 February 2013

Nigeria: Lassa Fever Marches On

Photo: Radio Okapi/ Ph. John Bompengo
Tests in a medical laboratory.

Lassa fever has threatened Nigeria for 44 straight years--and killed thousands of helpless people. Yet it continues to march on.

This year, at least three deaths--among them a healthworker--have been reported in Benue, prompting despatch of monitoring teams. Ondo will also be covered by teams investigating reported outbreaks.

The same outbreak was reported at the start of 2012, and it spread fast: in three months, the fever spread to 19 states.

At least 623 cases were reported and 70 people died--including three doctors and four nurses, according to epidemiological reports by the federal health ministry.

By last year's end, 1656 cases and 112 deaths would be reported in 23 states. The cases are a steady increase from 2011, which saw 1172 cases and 50 deaths.

For 44 years, Lassa fever has remained "an annual recurrent budget of death for the poor people of Nigeria because we have lived in a state of denial of the disease and handled it characteristic laxity, laissez-faire, negligence, sloppiness, slackness, disregard, triviality and freewheeling abandon," says Prof Oyewale Tomori.

The professor of virology at Redeemer's University also heads the expert review committee on poliomyelitis.

Despite the thousands of deaths from the fever, says Tomori, Nigeria is still unprepared to contain the disease, "waking up every year an outbreak is reported, running like a decapitated chicken in any which direction, and forgetting about the disease till another year another outbreak."

Naming the fever

The fresh outbreak this year calls attention to what the country is doing wrong. The Lassa virus--named after the Lassa community in Borno, where it was first described among healthworkers and locals in December 1969--is endemic in Nigeria.

"But there is not enough awareness of the endemicity of this disease in Nigeria," says Prof Dennis Agbonlahor, among researchers who first described the fever in Nigeria.

There is a large reservoir of the Lassa virus in rodents, and experts believe getting rid of rodents that carry the virus would "solve a large chunk of the problem," he explains.

The culprit Lassa virus is zoonotic--that is, it can infect both human and animals. And the African soft-furred rat, with a hairless tail, is the link to humans.

The animal frequently gets onto leftover food or food left to dry in the sun and open air. While eating, rodents may also urinate and defecate--and pass the virus onto humans who eat the contaminated food.

Doctors and nurses in contact with patients are usually among the first people to become infected and die.

Knowledge about the disease is growing but since the first outbreak in 1969, says Agbonlahor, "government has not been able to support a complete surveillance to know the distribution of the Lassa rat--where and how much of it in different parts of the country is still unknown."

(A similar surveillance for yellow fever has produced a model projecting as many as 101 million could be at risk in an epidemic--and has supported the case for mass immunisation.)

Also unknown is any major research ongoing about Lassa fever. Up until 2008, specimens from suspected cases were flown abroad for confirmation.

"We do not have a reliable, dependable, responsive disease surveillance system, not just for Lassa fever, but for any fever at all," observes Tomori.

He says Nigeria has refused to learn from 44 years of dealing with Lassa fever. "When our disease surveillance system wakes up, then we will be able to define the burden of the disease, by all its epidemiological parameters. Only then can we begin to map out what research activities to carry out, the results of which will guide our intervention strategies."

Since 2008, two centres have stepped in to fill the gap in laboratory diagnosis and research into the fever--Lassa Fever Research and Control Centre at Irrua Specialist Hospital, Edo, and Lahor Research.

The Irrua centre is claimed to have provided confirmation for all Lassa fever cases last year, but other laboratories set up failed on account of "lack of genuine government commitment, mismanagement and mis-application of funds by research staff in collaborative collusion with Ministry staff," remarks Tomori.

Nigeria's move to deal with the disease has focused on treatment with Ribavirin, an antiviral drug considered effective if a case is diagnosed early and effectively.

Last year, half a million vials of ribavirin were government response six weeks after the first reported cases in Ebonyi, "by which time, a doctor and three or four nurses had died while some other doctors were on admission at the Federal Teaching Hospital, Abakiliki," according to Tomori.

Alongside treatment, research considering candidate vaccines against Lassa virus are ongoing but are still inconclusive.

Care begins at home

There have been very few reports of the virus been exported, and only recently have cases emerged in neighbouring African countries.

Apart from some recognition in Guinea, Liberia, Sierra Leone, Lassa fever has managed to remain domestic--not what experts call an international disease.

Such domestic diseases do not get the attention of donor agencies that HIV/AIDS commands, says Agbonlahor.

"But when the disease is yours, should you wait for donor agencies to financially intervene? Why must they wait all the time for external bodies to come and assist them? You start intervening to the extent you can within your limited resources and then cry out for assistance."

Lassa fever has the greatest impact among haemorrhagic fevers--rivalled only by dengue. Up to 300,000 are infected annually in West Africa alone, and an estimated 5,000 of them die.

Most start getting symptoms between one and three weeks after contact with the virus. Fever is typical, as is pain behind the chest wall, sore throat, back pain, cough, abdominal pain, vomiting, diarrhoea. The face may swell, and protein may be passed out in urine.

The symptoms vary and make diagnosis difficult but there may also be bleeding in the mucosa--a lining that covers most internal organs--hence the term haemorrhagic fever.

Some experts have also described other neurological problems--including hearing loss, tremors and swelling of the brain due to infection--as likely signs of Lassa fever.

It is impossible to control rat populations, treatment is dependent on early diagnosis and vaccines are still a way off. Prevention is perhaps the strongest suit in the anti-Lassa arsenal, but is only possible "when you thoroughly know the epidemiology of the disease - natural host and habits, modes of transmission, as well other factors - environment, human behaviour," says Tomori.

"When you have such information, you are able to map out and implement interventions for prevention and control. The studies on the rodent host of the disease in Nigeria - their distribution, habits and habitats- are yet to be carried out."

Dealing with the rodents falls then to individual hygiene, says Prof Agbonlahor. "Rodent control is good but preventing them from coming to your home is better."

The same advice has come from public health experts for 44 years: stop rats from entering your home; avoid drying food on roadside close to bushes from which rodents can emerge to feed, urinate or defecate on foods; ensure leftover foods in the home are properly covered.

Simple enough, but deviating from hygiene, prevention, treatment describes what Pro Tomori calls his famous 19 words to describe the country's response to Lassa fever: "We have never been serious, nor are ever going to be serious about important developmental issues, including our health".

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