Zambezi outbreak mystery deepens

The mystery over the infestation deepened this week with experts still uncertain as to the cause, source and extent of the outbreak while suspicions turned on another organism – a virus.

The Zambezi River is one of Southern Africa’s two great rivers, spanning 2700 kilometers through eight countries and sustaining an estimated 40 million people before disgorging into the Indian Ocean.

A recent outbreak among catfish, breams and minnows has left scientists scratching their heads and their beards and scores of fish lovers are at the crossroads.

Should they or should they not eat fish given this unresolved mystery?

Last week, The Southern Times reported that a serious infestation among some fish in the back waters of Zambezi River had been detected amid fears it had spread and humans could be affected.

Although almost all experts interviewed when the story broke agreed that this was a regional problem which required a regional response, The Southern Times this week established that the region’s few fish parasitologists have not met and are not likely to meet over the matter any time soon.

Whereas Zambian scientists are said to be examining samples of infected fish and Namibia has also sent samples to South Africa, there is nothing co-ordinated at a regional level in response to the problem.

Botswana’s deputy fisheries director, Shaft Nengu, told The Southern Times on Wednesday that, to the best of his knowledge, there was nothing happening in his country in response to the reported outbreak.

“I am not aware of anything that has been done in the Chobe River. Certainly no-one is looking into this matter in Botswana. The last time I spoke to my colleague in Zambia (Charles Maguswi, Zambia’s director of fisheries), we agreed that this was a regional problem that required a regional response. I have not heard from him. I think the challenge is how to get people together,” he said.

Contacted for comment on Thursday, Namibia’s Permanent Secretary in the Ministry of Fisheries and Marine Resources, Nangula Mbako said: “We are still waiting for the results. As soon as we know we will issue a press statement that will benefit all stakeholders. Just be patient.”

Scientists and fish experts who spoke to The Southern Times this week expressed dismay at the lack of a co-ordinated response to the outbreak and challenged countries that share the Zambezi to walk their talk on regional integration and cooperation.

“This is a disgrace (that officials in countries along the Zambezi have not united in response to the outbreak). This is not something happening in an isolated fish pond. We claim to be highly educated yet we are not working together! As a result, solvable problems become a mammoth task and degenerate into a crisis. How ironic!” said one scientist on condition of anonymity.

Another scientist said: “I hope governments will work to protect the people through the responsible ministries in the meantime. This development has caused panic among people who live on the fish resources along the Zambezi. There is a need to reassure the public. To just keep quiet, is not the best option for anybody.”

Dr Percy Chimwamurombe, an ecologist, said there was need for urgent proper and co-ordinated research to establish what has gone wrong.

“My view is that people must abstain from eating fish until experts have established the cause and source of this infestation.

I love fish, but after seeing these pictures, it would take a lot of courage or foolishness – or both – to eat fish from the Zambezi before I know what is going on,” he said.

He added: “I have seen pictures like these in the past. Bacteria and viruses also cause similar lesions. Protozoan (bigger) parasites also cause lesions and sometimes they cause bumps so big on the fish that one can open them and see the parasites. If they are too small for the naked eye, the next course of action would be to investigate for microbial (bacteria and viruses) infection.

This can only be done in a laboratory using special media to culture growth of the micro- organisms in order to see them under a microscope.”

He said in extreme cases Deoxyribo Nucleic Acid (DNA) detection methods may be employed.

In order to establish the cause of an infection beyond doubt, one has to take the suspected causal agent and infect it into a healthy host and wait to observe similar symptoms.

Depending on the type of causal agent and the host’s response and resistance, the process can take weeks or even months while researchers wait for the suspected causal agent to build enough strength in the host to present symptoms.

“This is why it is critical for something to be done to protect public health in the interim,” he said.

Another scientist has recommended thorough boiling of fish if people cannot abstain from eating the fish altogether.

However, research by The Southern Times reveals that in some instances, even boiling may not be sufficient to guarantee people’s health and safety.

Some bacteria can survive thorough boiling.

Water boils at 100 degrees Celsius (depending on the height above sea-level), yet quite a lot of heat-resistant bacteria (in a class called thermophiles and extremophiles) have been known to survive temperatures as high as between 180 and 300 degrees Celsius.

In some instances to survive harsh conditions that include extreme heat, pressure and dryness, some (endospore-forming) bacteria will develop cysts (hard cell walls to protect themselves) and can survive common cooking procedures that include boiling, roasting and deep fat frying.

Clostridium – particularly resistant bacteria – has been known to survive canning.

“I think stakeholders need to sit down and find ways of warning people not to eat fish from areas where the outbreak is suspected until they know what is going on,” Dr Chemwamurombe said.

He said a worrying aspect of this outbreak was that it was “cutting across genera and families. It is like an outbreak affecting maize and sorghum in similar fashion. While the two are both grasses, they are not sexually compatible. Similarly, breams and catfish are sexually incompatible. They are so different, yet they are affected the same way.”

Professor Annamarie Avante-Oldewage, a Professor of Marine Invertebrate Zoology in South Africa, said added to their challenge of establishing what is causing the infestation is the problem of controlling it.

“How do you control it in the Zambezi, a natural environment?” she asked in response to a query by The Southern Times.

Dr Zeb Phiri, project manager for the Zambia-based Zambezi Action Plan Programme ( ZACRO 6.2), a two-year project to facilitate integrated water resources management in the Zambezi basin, said it might take a while before people know what is going on.

“There is no regional institution that has a clear mandate to respond uni-laterally to a crisis like this one. I know that at national level some countries are aware of this problem and are doing something, but it might take time,” he said.


December 2006
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