Leishmaniasis

The term Leishmaniasis comprises a group of diseases caused by different protozoan species of the genus Leishmania, and transmitted by the bite of certain species of sandfly.

Leishmaniasis is a disease of poverty as its victim is among the poorest. According to ranking after malaria it is a second mort prevalence parasitic disease.

The leishmaniasis causes considerable morbidity and mortality. It is the collective name for a number of diseases which have diverse clinical manifestations. There are three main clinical forms of Leishmaniasis: visceral, cutaneous and mucocutaneous.

While cutaneous leishmaniasis is characterized by lesion proximal to the site of the sandfly, visceral leishmaniasis is associated with immunepathology in the liver and spleen of the infected host.

Cutaneous leishmaniasis is caused by several species of Leishmania. Patients generally present with ulcers or nodules, usually on exposed parts of the body, such as the arms, legs and face.

Visceral leishmaniasis is an illness with prolonged irregular fever, splenomegaly and weight loss as it main symptoms.
Leishmaniasis

Etiology of malaria

The main cause of malaria is infection by the protozoan Plasmodium, which is spread by mosquitoes from an infected human host.

Malaria, among the most lethal of worldwide human infection is transmitted by the bite of an infective female Anopheles mosquito, which serves as the vector and definitive host.

Four species of Plasmodium infect humans: P. falciparum, P. ovale, P. malariae and P. vivax.

Of these species P. falciparum is the most virulence of the human malaria parasites and is responsible for bulk of the malaria related morbidity and mortality.

Perhaps the most important is the fact that many mosquito bites may not result in malaria, yet one can get malaria after a few bites or even without being bitten recently, depending on the mosquito spices that is biting.

The infection can be transmitted through exposure to infected blood and blood products, organ transplantation, or contaminated needles or by vertical transmission.

The most common clinical manifestation of acute malaria infection are fever, rigors, malaise, headaches, myalgias, and arthralgias. Splenomegaly is the most consistent physical finding.
Etiology of malaria

Plasmodium and malaria

Plasmodium, commonly known as the malaria parasite, is a large genus of parasitic protozoa. There are four main forms of human malaria. In humans, the causative agents are four species of plasmodium protozoa (single celled parasites), including vivax, falciparum, malariae and ovale.

The strains of malaria such as P. vivax, ovale, or malariae can infect the liver and persist in a dormant state for months, or even up to several years, after exposure.

Plasmodium vivax is perhaps the most prevalent of the four and is the species most frequently encountered in temperate zone. Plasmodium vivax is a tertian malaria since its cyclic paroxysm occur every 48 hours. Tertian mean that the symptoms occurs in three day cycles.

Plasmodium ovale causes a mild and very rarely fatal form of malaria. Similarly, Plasmodium malariae causes a mild infection. Plasmodium malariae is often referred to as ‘quartan’ malaria, meaning the fever and other symptoms run in four-day cycles.

Plasmodium falciparum strain is the most common type of malaria. It causes severe infections that kill millions of people every year worldwide. Clinically, Plasmodium falciparum are the most serious of the four, but it tends to run a shorter course without relapse.

Because of this risk of relapse, travelers to malarious areas are not allowed to donate blood for up to three years after returning.
Plasmodium and malaria 

What is parasitism?

Parasites are organisms that live in or on another living organism existing at the host organism’s expense, each individual parasite completing all or a major part of its life cycle in or on one individual of the host.

Parasitism can be defined as:
*Adapted to the physiochemical conditions of the host
*Utilized host nutrients in a manner compatible with host survival
*Minimizes the host immune response
*Has a life cycle synchronous with that of the host

The key features of parasitism are a close association and dependence on the host for food.

True parasitism is where the parasites live at the expense of their hosts and always have the potential to harm them, either directly, by depriving them of essential material or by destroying tissues, or indirectly, by damaging their hosts by the liberation of toxins.

Parasites are faces with dichotomous choice for infecting a new host. They can remain in place until a new host arrives or they can disperse.
What is parasitism?

Filariasis*

Filariasis
Filariasis is a helminthic infection found principally in tropical and subtropical areas in Africa, and in the South Pacific regions. The disease is transmitted from man through several genera and species of mosquitoes. The acute disease is manifested by recurrent chills and fever and by visible swelling or nodules of the lymphatics and redness of the overlaying skin due to parasitic involvement.

The illness usually subsides gradually with or without therapy. But in those who have been repeatedly infected and are chronically ill, the inflammatory reaction and scarring of the tissues surrounding the vessels may impede the flow of lymph and blood, and mammoth enlargement (“elephantiasis”) of the arms, legs, scrotum and breasts can occur. During World War II approximately fifteen thousand American military personnel became infected, but prompted withdrawal of these patients from the endemic zones prevented chronic disease and elephantiasis.

Filariasis was the first human disease described in which transmission through the skin was cause by the bites of arthropods. Doctor O. Wucherer (1868) found the embryonic filarial worms in the urine of a patient in Bahia, Brazil. T. R. Lewis (1872), working in India, observed the embryos in the urine and also in the blood, and Joseph Bancroft (1878) in Brisbane, Australia first described the adult worm. The parasite has been designated Wuchereria bancrofti.

The momentous discovery of the role of the mosquito in transmitting the disease was made by the Scotsman Patrick Mansion (1877) while he was practicing medicine in the Far East with the Chinese Imperial Maritime Customs. He became interested in the disease that confronted him, including filariasis. In that disease he recognized the parasites in peripheral blood films and also in postmortems material.

He noted the nocturnal appearance of the parasites in the peripheral blood and postulated that a blood sucking insect might be responsible for transmitting the infection. Manson proved the presence of the microfilaria in the mosquito Culex fatigans, thus supplying the missing link in the life cycle of the disease.
Filariasis