Leishmaniasis is a disease which is caused by bite of female Sand Fly. Sand Fly is a tiny insect belongs to Order Diptera, the same order in which mosquito and house fly exist. The scientific name of genus of this small creature is Phlebotomus spp. Sand fly sucks blood from humans and other domesticated and wild animals. In the course of sucking blood, it transmits parasitic protozoa (Leishmania) in host body that causes severe illness in humans.
The disease is existed in the six continents except Antarctica. The disease can be transmitted through two ways: zoonotic cycle involves various wild and domesticated animals like kangaroos, rats, rabbits, cats and dogs etc. and anthroponotic cycle which involves humans as reservoir. The later can be observed in highly populated areas.
Globally, Leishmaniasis is divided into multiple types. Among these, the important ones are Visceral Leishmaniasis (VL), Cutaneous Leishmaniasis (CL) and Muco-Cutaneous Leishmaniasis (MCL). Out of above mentioned, VL is the most threatening form resulting into the death of patient if not cured whereas CL is mild but the most usual form and can be lead to disability of the diseased organ if left untreated.
CL also called as Aleppi boil. In our languages, this is known as “Lahori Phora” or “Jahangiri Phora”. Mostly, adults and old aged people are vulnerable to this. Lesions development on the part of body where the fly bites, is common indication of the disease. According to World Health Organization (WHO) 1.3 million cases of CL are reported annually throughout the world. Most of the disease incidences are present in New World (Americas), the Mediterranean basin, the Middle East and Central Asia while in Pakistan it is present in all provinces of the country.
The other name of MCL is Espundia. This form of the disease destroys mucosal membrane of nose, throat and sensitive body parts of the patient. Majority of the reported cases are present in South American countries like Brazil, Peru and Bolvia. In Pakistan, 2 cases are reported from Sargodha (Central Punjab) and from Azad Kashmir the number is 8 thus, it proves the disease in country. This is the least understood form of Leishmaniasis than the others.
Visceral Leishmaniasis is commonly known as Kala Azar. Mainly, young children are susceptible to VL. The symptoms are enlargement of spleen & liver and uneven phases of fever. According to WHO, 200 000 to 300 000 deaths are reported annually throughout the world and this number can be even more because of weak reporting system as nations with high burden of disease are poor and have not developed case reporting system(s). More than 90% of the cases occur in India, Bangladesh and Ethiopia. In past years, 02 cases have been reported from Karachi in Pakistan.
Only female Sand Fly sucks blood from animals including man and causes disease transmission. Sand fly is a minute flying insect comprises of 1-3 mm in size, smaller than the size of mosquito which is usually 5-7 mm in size. The insect gets its daily life energy from nectar of flowers, fruits and honey dew secreted from the aphids (plant lice). Sand flies are poor fliers and they can move only 2 km away from their habitats however, can cover larger distances in case of wind blowing, due to their smaller size and low weight. Forest floor is its best resting site due to conducive microclimate. Sand flies prefer also to inhabit in abandoned nests of birds, reptiles and small rodents because of availability of rotting fecal material which is preferred food for their larvae. The vector is usually whitish to greyish in color while the body is fully covered with hairs. Mainly, sand flies are present in tropics and sub-tropics regions. Sand flies cannot be found in those tertiaries where the temperature falls below 15°C. These are usually divided in two groups: one is the species of new world and the other one is from old world. Scientifically, we call first group as Lutzomyia which is the main carrier of pathogen in Americas (North & South) and the second group as Phlebotomus, whose species are causing disease in remaining part of the world including Pakistan. The documented species are more than 800 which belong to the subfamily Phlebotominae out of them, ninety-eight species are reported to spread leishmaniasis in humans. Female fly can lay a small batch of eggs without sucking blood but requires blood meal for more egg laying. After emergence from pupa, male rotates its external genitalia within 24 hours to become sexually mature. Sometimes, copulating occurs on the host where the female is taking blood. There is no preferred timing for its biting like in case of mosquitoes and can attack at any time. But at the time of dusk they attack more. They always move in groups. The disease-causing agent can be found in dense vegetation, wall ceilings and in tree holes etc.
Basically, there is no vaccine or oral medicine for CL. The only treatment for CL is a glucantime injection which costs for 800-1000 Rs. Usually for treatment of one ulcer, on the average seven injections can be used which may be increased depending on the condition of patient. For the treatment of other types there is no specific medication available. So, the only way to control the disease is to control the population of vector sand fly.
The vector can be controlled by destruction of their habitats / breeding sites like soil in human dwellings, rotted manure, garbage in the street, hollow trees, roots of large trees and abandoned nests etc. All the above-mentioned activities involve community participation. This approach is one of the cost effective and an easiest way to get rid from number of diseases. For successful control of disease or vector, the efficient method is to mobilize communities by sharing true knowledge and by bringing change in human behavior. The other way is to maintain cleanliness and hygienic conditions which is also not possible without involvement of people. Cleanliness refers to cleaning of their homes, surroundings, avoidance from throwing garbage into streets and appropriate disposal of debris. The other preventive methods are secondary in nature which includes use of insect repellents like DEET, mosquito nets, keep body covered, use of light color dress and avoid passing through the endemic areas of vector infestation.
By adoption of above mentioned preventive methods, we can save ourselves and other people from biting of sand flies consequently protecting the society to get Leishmaniasis.
This article is collectively authored by Syed Haroon Masood Bukhari and Dr. Unsar Naeem-Ullah.Department of Entomology, Muhammad Nawaz Shareef University of Agriculture, Multan.