Tropical diseases? Not your problem? Oh yes they are and not just because of the need for anti-malarials when you go on holiday.
I heard about some of the problems and successes at the first International Meeting on Tropical Medicine to be held in the University of Peradeniya in Sri Lanka. I went along and learned a few thing of general interest.
Dengue or break bone fever is due to an Arbovirus, that is a virus spread by arthropods (insects, spiders, millipedes and Crustacea but usually mosquitoes). It is called break bone fever because that is what it feels like. If you survive to day 6 you will probably recover. Up to 10% die.
Dengue (pronounced Dengy here in Sri Lanka) continues to spread rapidly through the tropics and there are now 30 times more cases than 50 years ago. You are more likely to catch this than malaria in many countries.
There is no vaccine – or – there was no vaccine until last week when a group from Mexico announced successful preliminary trials. This was of major interest at the conference and, to its credit, the Sri Lankan government has already begun to negotiate purchasing supplies.
Doctors who study disease word wide speak of ‘Global Health’ and also of ‘One Health’ meaning that disease does not respect national borders and the health of animals is as important as that of man for animals and man share many infections.
Mass population movements by immigration of people from the middle east, by air travel and due to other pressures are matched by mass migration of animals and insects due to global warming.
Global warming is real even if you do not agree how it is coming about. Then there are mass movements of animals, alive or dead, as part of food distribution. Add in irrigation schemes which change the distribution of insect vectors of disease and you appreciated the need for vigilance.
One instance told to me by the Professor Santiago Mas-Coma, President Elect of the International Federation of Tropical Medicine, was the recent overwhelming of some hospitals and doctors by the influx of migrants into Germany.
Suddenly these doctors had to diagnose and treat diseases we regard as Dickensian and no longer a threat. Scabies, mites, fleas, bed bugs, intestinal worms, malnutrition and tuberculosis. Only a few older doctors have ever seen scabies.
In living memory, a number of new diseases have arrived.
Think of HIV and AIDS, BSE (mad cow disease), Avian ‘flu, Ebola, SARS (Severe Acute Respiratory Syndrome) and Lyme disease. Many of these diseases are viral and we know how viruses can change and mutate then burst out as a new epidemic.
We know ow to stop epidemics but we are poor containing them. We knew how to stop Ebola and eventually we stirred ourselves to do it but there were many inexcusable delays, bureaucratic muddles and reluctance to fund the task.
‘One Health’ is another new concept. Health matters whether it is you, your pet, plants or the animals you want to eat. Many tropical diseases do not spread to humans but they cause abortion, sickness and death in animals. The result is malnutrition, sickness and starvation in the human owners.
Do you remember the Foot and Mouth outbreak in 2007? There were outbreaks in 2001 and in 1967 as well. We got on top of it eventually but it cost us most of our ruminant livestock and pigs. The cost to farmers was far more than financial. The disease is still there, somewhere.
West Nile Fever
West Nile Fever is an interesting viral disease discovered in 1937 and troubling humans little in the West Nile area. A small proportion of humans get encephalitis and a few die from it. The virus is prevalent in songbirds but they suffer no disease, crows and raptors however do get sick. Mosquitoes spread the virus to man and to horses which become very sick and infertile.
Suddenly West Nile virus turned up in New York in 1999 and within 5 years had spread throughout the US, Canada, Mexico and the Caribbean. So far there is no vaccine.
West Nile Fever Encephalitis is a problem in Texas and a few other states. A mosquito with the virus probably flew in to New York in someone’s luggage.
There has been other good news apart from the Dengue vaccine. Do you remember Smallpox? The last small epidemic in England was in 1962. I was a medical student then and was sent out to help with a mass vaccination program. Now the disease has been totally eradicated worldwide.
Polio has almost gone. It still exists in a few pockets in the world where religious teachings and political venality have prevented effective vaccination.
Rabies is under control. Chipping and vaccination of dogs helps. Dropping food containing vaccine helps limit the spread in feral dogs, foxes, bats, jackals and mongooses. There is an effective post exposure vaccine for humans but you have to be treated within 24 hours.
Neglected Tropical Diseases
Tropical diseases have been neglected, and there is a scientific journal devoted to neglected tropical diseases.
I, with others, recently published an article about snake venom there. There is a movement northwards of tropical diseases. Leishmaniosis is moving from North Africa into other Mediterranean countries, aided in part by the Schengen agreement which applies to pets as well as humans.
Schistosomiasis has reached Sardinia.
Third world and emerging countries have not had money to buy drugs and vaccines. Many vaccines have to be kept cool and injected. Often several doses are given a few weeks apart. To get refrigerated drugs and sterile syringes to isolated jungle villages is not easy.
It is economically more worthwhile for a drug company to produce a better aspirin for your headache than to produce a life-saving vaccine which patients cannot afford to buy. There is a moral drive to produce tropical medicines but mostly the bean counters are in control.
Now many tropical countries are economically important. Pharmaceutical companies are finding it difficult to discover new drugs for the western world so they are beginning to turn their attention to the third world and tropical diseases.
Dengue – A virus fever spread by mosquitoes. Up to 10% mortality.
Ebola – A viral disease with up to 90% mortality.
Foot and Mouth Disease – A virus infects cloven hoofed animals. Rarely affects humans. Hand Foot and Mouth disease sometimes seen in children is a different virus.
Leishmaniosis – A small parasite spread by a sand fly. Causes skin ulcers and liver disease.
Lyme disease – A bacterial disease spread by tics from deer.
Malaria – Everyone knows this protozoan is spread by mosquitoes. There is still no satisfactory vaccine despite our efforts.
Rabies – A viral disease 100% fatal in humans. Spread from dogs usually.
SARS – Sudden acute respiratory syndrome. Kind of severe flu virus with high mortality. Eradicated but a similar virus may recur.
Schistosomiasis – Caused by a worm hosted in water snails.
Smallpox – Eradicated worldwide thanks to initial efforts by Edward Jenner of Gloucestershire starting in 1796.
West Nile Fever – One of several arbovirus diseases causing encephalitis.
Post Series: Dispatches from Sri Lanka, by Mike Sedgwick:
- Tropical Diseases – What You Need to Know
- Dispatches from Sri Lanka – The Tunnel in Kandy
- An Unusual Carol Concert in Sri Lanka
- Christmas in Sri Lanka: 9 Things in England I’ll Miss This Christmas
- Agricultural Restaurant in Sri Lanka
- Back to Sri Lanka
- Bats and Hallowe’en
- Dispatches From Sri Lanka
- Kandy Lake vs Chandler’s Ford Lakes
- Self-Employment In Sri Lanka
- Sri Lankan Wedding
- Sri Lankan Food
- There’s Some Corner Of A Foreign Field
- The Cultural Triangle of Sri Lanka
- This Is the Record Of John
- Tuk-tuk: My Transport Of Delight
- Life On The Road
- Commonwealth Games In Kandy
- A Temple For A Tooth?
- Dawn Train Down The Mountain To Colombo
- Traditional And Modern Medicine in Sri Lanka
- Ancient Vedda Tribe Becoming Extinct
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