Human induced changes in emerging and re-emerging infections

Dr. Viraj Peramuna

Jhon M. Last Emeritus Professor of Epidemiology and Community Medicine University of Ottawa in an article on - new causes for new diseases in pointing out the human factor involved in them says:

"For better or worse, the risk of many infectious diseases is influenced by human alteration of local, regional, or global ecosystems".

Global warming

The greenhouse effect, mainly due to fossil fuel combustion, is changing the world's climate. Mosquitos that carry malaria, yellow fever, dengue and viral encephalitis are extending their range into temperate zones, higher altitudes of tropical regions and large cities like Nairobi and Harare. By the middle of the 21st century there may be several hundred million more cases of malaria each year, as a result, many of them in regions now free of malaria.

Not all ecological changes are caused by human activities. The tropical Pacific Ocean current El Nino undergoes period warming. In the early 1990s, such a change was accompanied by the proliferation in coastal waters of South America of blue-green algae. These harbour the cholera vibrio which can survive for lengthy periods in various forms of plankton.

Tuberculosis has always flourished in conditions of poverty, overcrowding, poor nutrition and illiteracy; HIV infection spreads when women must resort to prostitution in order to survive, and when intravenous drug abuse with needle-sharing occurs.

Finally, there have been several recent cases of a variant of Creutzfeld-Jakob diseases, a progressive and fatal degenerative brain disease, in the United Kingdom and France.

These cases are thought to be due to exposure to an unconventional infectious agent belonging to the group responsible for transmissible spongiform encephalopathies (TSE).

One of these, bovine spongiform encephalopathy (BSE) - a disease of cattle - is thought to be caused by the agent of scrapie, a TSE of sheep. Sheep's offal has been used to prepare protein supplements fed to cattle.

Although not yet proven, the circumstantial evidence is persuasive and worrying: the infectious agent seems to have passed from sheep to cattle to human beings. This may be an example of the consequences of human interference with natural processes - in this instance feeding animal protein to a vegetarian species.

Cleaning up dirty water and keeping it clean

In many parts of the developing world, drinking-water is collected from sources outside the home. It may be contaminated at the source or during storage. Strategies to reduce waterborne disease transmission must safeguard against both possibilities.

New products allow families to disinfect drinking-water immediately after collection, and newly designed narrow-mouthed, closed storage vessels prevent recontamination.

This two-component prevention strategy is a practical and inexpensive way for households and communities that lack safe water to protect themselves against a variety of waterborne pathogens, and can progressively decrease waterborne diarrhoeal diseases.

The method has been tested in various parts of Bolivia by the United States Department of Health, the US Centers for Disease Control and Prevention, the Pan American Health Organization and the United States Agency for International Development.

Well accepted, it has significantly improved the quality of stored water and brought about a decrease in diarrhoeal disease, especially among infants under one year.

The method could be an effective took against waterborne diseases such as typhoid fever and cholera in such settings as day care centres and old people's homes, and could be used during festivals.

Clinics, schools and even street vendors are attractive potential targets for this intervention, which encourages the washing of hands, foods and kitchen utensils in order to reduce diseases transmitted by personal contact or contaminated food.

The next generation of vessels, currently being pilotested among Guatemalan street vendors, will have a built-in soap dish to promote hand-washing. With the commitment of communities, ministries of health, United Nations agencies, non-governmental organizations and private industry, this low-cost effective intervention could be implemented on a broader scale.

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Medical Crossword No. 32

Entries from doctors too

We are pleased to note, that more and more doctors too, among other professionals are now sending entries to our - Healthwatch Medical Crossword Competition.

In the first batch of entries we received for the Medical Crossword No. 32 based on the theme - Physical Activity - we had ten entries from the doctors.

Among them there was one young doctor from Kurunegala Dr. Arjuna Ellepola (31 yrs) who had sent entry for his wife too - Manori Tharanga Ellepola. When we spoke to him to find out whether him sending an entry meant that he found the Medical crossword feature the only such feature in the English daily newspapers here, one of our own creations in our health education programme in a daily press, he said "yes, I must congratulate your Features Department for this innovative approach for health education of the readers.

As doctors we find it interesting too, as it relates to our profession, promoting preventive health in an interesting way."

Student Entries

This time we had student entries from 17, 18, 19, 20, 22, 23, 25, 26-year-old from Kandy, Kohuwala, Colombo, Nugegoda, Mattumagala, Panadura.

Among them Anupama Siribaddana 17 years, Grade 12, Mahamaya Girls School, Kandy. Y. Risla 18 yrs G. S. Convent, Colombo. A. F. Kariyapper 22 yrs.

Undergraduate from Kohuwala. A. Dharshika 22 yrs Medical student from Colombo 6.

From Company Chairman and others

We had entries from a Company Chairman Mr. Joe Aloysius 78 yrs. A young business analyst Miss Jilsha Tissera 24 yrs from Bambalapitiya.

Attorney-at-Law. An entry from a lawyer Christopher Cadiramanpulle (71 yrs.) Retired Principal - An entry from a retired school Principal Rani Fernando 76 yrs.

From 80-year-olds

We had 5 entries upto now from the 80-year-olds. Among them are E.C. Jayasinghe 82 yrs. from Nugegoda. Rose Samarasinghe also 82 yrs from Nugegoda. Quintus Jayawardena 84 yrs from Ahangama and R.M.L. Ratnayake 84 years old from Matale.

Entries from Housewives

Among entries from housewives we found a good number from those in the age group of 70s - 70, 75, 77, 78, 79, and also those in the young age group of 30s - 34, 35, 38. Our Medical Advisory Panel is compiling statics of those who are sending entries for the Medical Crossword for a study.

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Gastrointestinal Decontamination in Poisoning

Prof. Ravindra Fernando, Faculty of Medicine, Colombo.

Acute poisoning is a medical emergency. Gastrointestinal decontamination is a commonly practiced measure in the management of poisoning. This includes any method which aims at reducing the absorption of an ingested poisonous substance.

Methods of gastrointestinal decontamination include inducing emesis (vomiting), administering activated charcoal, gastric aspiration and lavage.

These methods should only be considered following a full medical assessment by the physician and once the patient's acute condition is stabilised. It should only be considered in patients who are able to protect their airway and who have taken a potentially dangerous amount of a poison. Secretions should be sucked out.

If cyanosed, oxygen must be given. If the respiration is impaired, intubation and assisted ventilation should be considered.

Patients who are most likely to benefit should have the decontamination within 2 hours of ingestion of poisons.

Clear evidence for clinical benefit from gastrointestinal decontamination has not been shown. The best evidence of benefit is from activated charcoal. Different Methods of Gastrointestinal Decontamination in Poisoning

Activated Charcoal

Activated charcoal is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms. These so-called activated charcoal particles are widely used to adsorb poisonous substances.

When certain chemicals pass next to the carbon surface, they attach to the surface and are trapped. Adsorption of poisons to activated charcoal can reduce absorption of a wide range of poisons from the gastro-intestinal tract. The effectiveness of activated charcoal decreases with time and is greatest if administered within one hour of ingestion.

This is widely used for poisoning with drugs. It can be effectively used for pesticides and most other substances where the toxic dose is relatively small. Some toxic substances not effectively adsorbed by activated charcoal are acids, alkalis, iron, lithium, alcohols and glycol.

The dose is 1 g/kg for all ages

For paraquat (a pesticide used in Sri Lanka) poisoning, Fuller's earth is the adsorbent of choice. Activated charcoal may also be used. Activated charcoal is contraindicated if the patient's consciousness is impaired and they are unable to protect their airway.

Multiple-dose activated charcoal (MDAC) therapy (repeated administration of oral activated charcoal) enhances elimination of poisons and may reduce absorption of controlled release drugs and oleander seeds.

Gastric aspiration and lavage

We see this method being used commonly in a lot of hospitals as the first measure, in all patients coming after ingestion of any poison. But, gastric lavage should not be routinely used in all patients.

If and when it is done the doctor must take personal care to ensure that all precautions are noted and complications are prevented by close care and monitoring by adequately trained staff.

It cannot be overemphasized that there is mounting evidence to doubt the clinical benefit of gastric lavage. Most comparative studies show it to be equivalent or inferior to activated charcoal.

To be continued