By a Protozoan, Plasmodium. There are several species of Plasmodium with different periods of incubation :
- Causes Benign Tertiary Malaria.
- Incubation period is 13 – 15 days.
- Fever recurs after every 48 hours.
2. Plasmodium Malariae
- Causes Quartan Malaria.
- Incubation period is 28 – 30 days.
- Fever recurs after every 72 hours.
3. Plasmodium Falciparum
- Causes malignant tertiary malaria.
- Incubation period is 12 days.
- Affects brain and recurs every 36 hours. It is usually fatal.
4. Plasmodium Ovale
- Causes mild tertiary malaria.
- Recurs after every 48 hours. Incubation period is 14 days.
Disease spreads by certain species of Anopheles mosquito (only female anopheles)
Life Cycle of Plasmodium is completed in 2 hosts :
- Man : Primary Host
- F. Anopheles : Secondary Host
After incubation period, temperature of body rises with a feeling of chill, signs of headache and nausea.
Then temperature falls (symptom : sweating). The above symptoms are repeated after every fixed hrs depending upon the species.
Certain fishes like cat fish, Gambusia and aquatic birds eat mosquito larvae.
Quinane, a product of Cinchona tree, is administered for Malaria.
Kala Azar (Leishmaniasis)
Caused by Leishmania donovani.
It is spread by sandfly (Phlebotomus) and characterized by enlarged spleen and liver with high fever.
Kala azar is also known as dum dum fever.
Caused by Giardia intestinalis (first parasitic protozoan known). It inhabits upper part of small intestine (duodenum and jejunum).
Characterized by mild diarrhoea involving passage of pale, bulky, foul smelling and greasy stool.
Caused by different species of Trypanosoma.
Main disease is Gambian fever or West African sleeping sickness, the vector of which is Tse tse.
Amoebiasis (Amoebic dysentry or Enteritis)
- Caused by Entamoeba histolytica.
- Characterized by abdominal pain, alternating diarrhoea and constipation, stool with blood, mucous and mucous membrane pieces.