Mosquito control and prevention of Filariasis .

 Amongst the numerous species of blood sucking arthropods that hurt man and other warm blooded animals,mosquito is most eminent. Mosquitoes have a world wide distribution, being seen in tropics, in the temperature regions and also in the cold circles like arctic areas. They have been found breeding in deep mines,underground tunnels and have been found at altitudes as four thousand meters above sea level. There are about 2400 species of mosquitoes in the world, out of which only 10 species of medical importance. In India only the Anopheles,Cu lex,Aides and Monsoonal are the vectors causing malaria, dengue,filariasis, yellow fever and certain encephalitis.

MOSQUITOES: We, human being have different blood groups. No matter whatever the blood group, mosquitoes like to feast on human blood and mosquitoes do not have any blood groups of their own. In fact they do not have any blood at all. They have body fluids only,but it is not blood, it is called hemolymph, and different from human blood. It does not have RB C in it.This absence makes a huge difference, because RB C determine the blood group of human beings. In other words, those possess neither blood nor have any blood group.The females of all medically important mosquitoes are blood suckers as they require a blood meal for the development of eggs.

MOSQUITO CONTROL: ANTI-ADULT MEASURES.

Personal protection against their bites helps these measures in the control of disease. Anti-adult and anti-larval measures are 2 most important mosquito control measures. Space spraying of insecticides can be used against adult mosquitoes for controlling the transmission of malaria or to reduce density of adult mosquito population.The object is to destroy infected vector mosquitoes during the incubation period of the parasites by spraying 0.1 percent pyre thrum extract.Aerosols are also used as spare insecticides under emergency conditions.

PERSONAL PROTECTION AGAINST BITES.

Use of mosquito net is the most effective personal protective measure. Protective clothing and screening of the houses and hospital wards also can be practiced from mosquito bite.

ANTI LARVAL MEASURES.

Prevention of breeding places ,destruction of larvae, in breeding places by oiling, praying of BHC on water acts as a contact and oral poison to mosquito larvae.A weekly dose of 70 mg per sq.mtr is sufficient to keep the water free from larvae.A 5 percent watery solution applied at the scale of 3 liters per acre will ensure this dose.In this dosage it is not harmful to fish, cattle or crop. Fish of Gambusia affinis are useful in dealing with larvae in wells, gardens tanks,  ornamental tanks, fountains and small permanent pools. It can multiply in artificial tanks. It flourishes under different climatic conditions and equally thrives in deep and shallow waters and changes in the salinity of water dose not effect its survival. If used large fish in fire fighting tanks they may block the engine hose or nozzle. It is, there fore, in fire fighting tanks observance a dry day and use of BHC or DDT as larvicide is the only method of larval control.

FILARIASIS.

It is a mosquito borne worm infection of lymphatic and connective tissues of man by round worms of the family Filarioidae. Sudden clinical signs and symptoms are caused by enlargement of lymphatic glands and inflammation of tissues and organs swelling of testes and genital parts and non genital elephantiasis due to blockage of lymphatics. Diagnosis is confirmed by microscopic examination of a night blood smear. The disease filariasis in man is due to Wuchereria Bancroft and Brugia malayi. there are many other tissue filariae parasites to animals, but they have not been seen parasitising man. The adult worm is 5 to 8 cm long,female are longer than the male. Male and female live together coiled or knotted in lymphatic glands, lymphatic ducts and connective tissues. It may live for long periods ,even up to 12 years. The embryo or  microfilaria is about is about 280m and lives for a 15 days if not picked up by the mosquito vector.They are regular active in midnight and appear in the peripheral blood stream.  Mosquito,  Culex fatigans is the main vector of filaria in India.Incubation period in man is about 9 months to 2 years or may be longer;normally a period of one year is required for symptoms of lymphatic blockage to make their visibility; after introduction of larva in man. The incubation period in mosquito is 10 to 14 days. Man possess no natural immunity.

PREVENTION AND CONTROL.

The important measures for prevention and control of infestation in the community are mosquito control at all stages of their life cycle,personal protection from mosquito bites, and personal protection has a value during night, dusk, dawn, but vector species may bite during day time also.

Endemic simple goitre and its prevention and control

Introduction

It is an expansion of a simple thyroid gland with out toxic display is called simple endemic goitre or in other words,a morbid enlargement of the thyroid gland.A normal thyroid gland takes up a space of about 5 cm square across the front of the wind pipe( trachea) rings below the cricoid cartilage.It is a few mm in thickness at its central part. Normally the gland is not visible nor palpable. It becomes palpable only when it is enlarged 5 times all round. So goitre can not be diagnosed before the gland is 5 times expanded.It regulates body growth, metabolic rate, the development of brain, sexual development at adolescence, maintain normal pregnancy and milk lactation. These are carried by its internal secretions(hormone) called thyroxine. This gland has a chemical attraction for iodine. Iodine is necessary for the reduction of thyroxine.

Prevelance(Epidemiological distribution)

Local inhabitants in the foot hills of Himalayas up to the height of 6000 to 7000 ft,suffer from endemic goitre. Simple goitre becomes endemic if the soil in an area is lack of iodine and hence results in low iodine content in water and vegetables and products grown there upon. Such goitre areas are found in Swiss, french,Austrian and Italian Alps and rocky mountains in United states and also found in Himalayan regions.The distribution of endemicity in these areas is, however belonging to focus, sometimes the goitre pockets adjourns the non goitre areas, separated by only a water shed or supply of salt.

Causes of the simple goitre

Simple goitre develops if enough iodine is not made available to the thyroid gland or if the demand increases as in puberty for growing tissues or if the thyroid can not utilise the available iodine. Thyroid may go deficient of iodine if it is deficient in food, water, milk if it is not properly absorbed. It may less in food and water if it is less in soil or bacterial pollution of water or cyanates in vegetables. The deficiency in hill areas may also be low consumption of common salt due to non availability or low bodily requirement due to the cold atmosphere. In mountainous areas the soil is also poor in sodium or potassium salts. If the soil is salt free due to ancient deposition of ice on it which has left silt-free salt dry, for example, in North America, St.Lawrence and lake city area and Oregon.

Stages of goitre.

Simple goitre starts in childhood due to lack of iodine and fully develops by the age of 30 years after that it becomes nodule or swelling.The cells increases in size and numbers in the attempt to produce enough thyroxine out of diminished iodine contents,when it is enlarged more than about 5 times.It is palpable and called first stage. according to expansion it has 4 stages and further enlargement of swelling becomes irregular and nodular,then terned as nodular goitre,and this stage may be reached after 30 years of age.hence there are 2 groups,first group is called non nodular and second is called nodular stage.

Effects of goitre

Simple goitre may not cause any ill effects,but has a potential of becoming nodular and then its big size it may cause disturbances in breathing due to pressure on the nerve.When it may become a toxic goitre and rise to the signs and symptoms of Graves disease.Congenital or infancy defects are more common in goitrogenic tracts. Nodular goitre may turn to malignancy in advanced ages.

Causes of iodine deficiency in regional areas

Genetic character of the local population, deficient iodine in vegetable products due to presence of cyanates, bacteriological pollution of water supplies causing iodine deviation,high magnesium and calcium hardness of water and lack of iodine in the soil and tracts.

Prevention,control and remedy

Administration of a minute quantity of iodine from childhood prevents goitre in endemic areas. Iodized salt supply to population in goitrogenous areas prevents endemic goitre from developing the community. It is proposed by mixing and and then grinding common salt with 0.02 percent of potassium iodide or 0.002 percent of iodate. It is noted that even proprtions of lower than this will prevent endemic goitre. Eltraxin(sodium levo-thyroxine)is used with results for rapid reduction of enlarged goitre. Uncomplicated cases may be treated with Eltroxin with out admission to hospitals,but those cases showing toxicity or other complications should be admitted to hospitals.All treatments should be given under the supervision of registered medical practitioners. Monthly or periodical check up for the detection of the early goitre in endemic areas also be carried out as preventive and control measures.

PM Kutty