Tuesday, August 31, 2010

Tips for prevention of breeding of Aedes mosquito in your urban neighbourhood

Dengue fever is an acute febrile illness which can be life threatening.The WHO says some 2.5 billion people, two fifths of the world's population, are now at risk from dengue and estimates that there may be 50 million cases of dengue infection worldwide every year.
Dengue is transmitted by Aedes mosquitoes, particularly A. aegypti and A. albopictus.So it is very important for us to know about these mosquitos and to learn how to prevent its breeding in our neighbourhood.

Dengue Virus Transmission

Dengue viruses are transmitted to humans through the bites of infective female Aedes mosquitoes. The mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for eight to ten days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus for the rest of its life. There is no way to tell if a mosquito is carrying the dengue virus. Infected female mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission, but the role of this in sustaining transmission of the virus to humans has not yet been defined.

Aedes aegypti goes through a complete metamorphosis with an egg, larvae, pupae, and adult stage. The adult life span can range from two weeks to a month depending on environmental conditions. The life cycle of Aedes aegypti can be completed within one-and-a-half to three weeks

After taking a blood meal, female Aedes aegypti mosquitos produce on average 100 to 200 eggs per batch. The females can produce up to five batches of eggs during a lifetime. The number of eggs is dependent on the size of the bloodmeal. Eggs are laid on damp surfaces in areas likely to temporarily flood, such as tree holes and man-made containers like barrels, drums, jars, pots, buckets, flower vases, plant saucers, tanks, discarded bottles, tins, tyres, water cooler, etc. and a lot more places where rain-water collects or is stored. The female Aedes aegypti lays her eggs separately unlike most species. Not all eggs are laid at once, but they can be spread out over hours or days, depending on the availability of suitable substrates. Eggs will most often be placed at varying distances above the water line. The female mosquito will not lay the entire clutch at a single site, but rather spread out the eggs over several sites.

The eggs of Aedes aegypti are smooth, long, ovoid shaped, and roughly one millimeter long. When first laid, eggs appear white but within minutes turn a shiny black. In warm climates eggs may develop in as little as two days, whereas in cooler temperate climates, development can take up to a week. Laid eggs can survive for very long periods in a dry state, often for more than a year. However, they hatch immediately once submerged in water. This makes the control of the mosquito very difficult.

Prevention of breeding of Aedes mosquito

Aedes mosquito lay their eggs in clear,clean water and not in contaminated water.As they fly only a few metres their breeding place is usually in our house itself.

Most common breediing places and tips to prevent breeding

Water storage tank/cistern ---should have mosquito proof lids
water coolers/collection pans in Fridge/ACs ------ water should be drained out periodically 

Drum   ------tight lids
Flower vase with water  [least in brass vase]----------change water frequently,use sand
Potted plants with saucers ------- change water frequently
Ornamental pool/fountain ---------water changed once a week
Roof gutter/sun shades------------check frequently for drain block
Animal water container----------- empty and clean periodically
Ant trap--------------------------use oil/salt
Used tyres-----------------------keep it under roof
Discarded large appliances-------bury or keep it under roof 
Discarded buckets,plastic cups,tin cans etc-----bury

Whenever piped water supply is inadequate and available only at restricted hours or at low pressure, the storage of water in varied types of containers is encouraged, thus leading to increased Aedes breeding.It is essential that potable water supplies be delivered in sufficient quantity, quality and consistency to reduce the necessity and use of water storage containers that serve as the most productive larval habitats.

Chemical and biological agents can also be used for prevention of breeding of Aedes mosquito.


Saturday, August 14, 2010

'Superbug' scare. Myths and facts

A scientific article in the Lancet has created big commotion in the media both in India and outside.It is being said that a bacteria which is resistant to all known antibiotics is wide spread in India and Pakistan and is being spread to other countries including U.K through medical tourism.This bacteria termed the 'superbug' is supposed to bring an end to the antibiotic era. Indian Government has come out with a clarification saying the media scare in UK is unwarranted.
Let me try to separate facts from myths in this issue.
Fact 1
WHO has identified antibiotic resistance as one of the greatest threats to human health. In the European Union (EU), about 25 000 patients die every year from infection with multidrug-resistant bacteria, and such infections result in health-care costs and lost productivity totalling at least €1·5 billion per year. Methicillin-resistant Staphylococcus aureus alone infects more than 94 000 people and kills nearly 19 000 in the US every year, more deaths than are caused by HIV/AIDS, Parkinson's disease, emphysema, and homicide combined.
Fact 2
Bacteria with Carbapenemase  activity is a fast emerging threat in the field of antibiotic resistance all over the World as you can see from this article. India is actually a late entrant in this field.
Fact 3
There are 4 classes of Carbapenemase A,B,C and D.Each have different sub groups.So there are a large number of such bacteria producing different Carbapenemase isolated from all over the World.
Fact 4
New Delhi metallo-beta-lactamases[ NDM-1] belonging to B sub group of Carbapenemase was first detected in a Klebsiella pneumoniae isolate from a Swedish patient of Indian origin in 2008.It was given such a name assuming that the patient got it while hospitalized in New Delhi.
Fact 5
Further study in India indicated that NDM 1 enzyme producing bacteria are fairly common in a tertiary hospital in Mumbai.
Fact 6
In short NDM1 enzyme  is the major cause for antibiotic resistance in Ecoli and Klebsiella species in India.In other countries enzymes are different and are named differently like    VIM-1 (for “Verona integron-encoded metallo-β-lactamase” first isolated in Verona, Italy,)       SPM-1 (for “Sao Paulo metallo-β-lactamase”),         GIM-1 (for “German imipenemase”)    SIM 1 (for Seoul imipenemase)   etc.
Fact 7
The Lancet article in question is only about NDM 1 producing bacteria. It is a good attempt to find out the extend of spread of antibiotic resistance in bacteria in India.
Fact 8
It showed NDM in UK not only in those who had surgical procedures in India but also in many who have never visited India..Out of the 37 samples with NDM1 collected in UK, only 17 samples had history of travel to India or Pakistan.
The article in Lancet says
'It is disturbing, in context, to read calls in the popular press for UK patients to opt for corrective surgery in India with the aim of saving the NHS money. As our data show, such a proposal might ultimately cost the NHS substantially more than the short-term saving and we would strongly advise against such proposals'.
This is an unscientific comment not based on any data.The authors have not proved that NDM 1 enzyme producing bacteria in UK was imported from India. More than 50% of patients in UK detected to have NDM 1 has never traveled to South Asia.Also the comment is not taking into consideration other groups and sub groups of Carbapenemase enzyme producing bacteria which are more prevalent in UK than in India.

         The author of the article in Lancet seems to show undue haste in blaming medical tourism for antibiotic resistance in UK.

It is true that Indian health system abuses antibiotics like most other 3 rd World countries.While protesting the unfair conclusion of the author of the article let us hope that the concerned authorities will open their eyes to the lack of antibiotic policies in most health care centers of India and implement strict regulations so that patients both native and foreign are protected from emergence of resistant bacteria.