The disease causing protozoa are called pathogenic protozoa. Such protozoa are met within all the classes of this phylum. In man alone, more than 25 types of parasitic protozoa are found. Depending upon the location inside the host body, these are divided into various groups.
These are:
Parasites of Mouth:
i. Entamoeba Gingivalis:
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A Sacrodina lives in the tartar of teeth and pockets of gums. They probably aggravate pyorrhea in man. They are also found in dogs and cats. The human infection is caused by kissing.
ii. Trichomonas Tenax:
A flagellate also lives in pus pockets formed between teeth and gums. It causes pyorrhea. It is transmitted during kissing.
iii. Leishmania Brazxliensis:
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A flagellate lives in the ro-nasal mucous membrane. It causes espundia. The infection is transmitted to man by the bite of sand-fly.
Parasites of Digestive Tract:
i. Entamoeba Histolytica:
It lives in the colon of man, sometimes in dogs and cats. It causes amoebic dysentery. It may reach liver, spleen, lungs and liver and causes amoebic abscesses. Infection takes place by swallowing of cysts.
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ii. Trichomonas Hominis:
It lives in large intestine of man, monkeys, cats and dogs. It causes diarrhea and dysentery. It is transmitted through infective cysts.
iii. Chilomonas:
It lives in large intestine of man and causes diarrhea and allied troubles. Transmission is by means of infective cysts.
iv. Giardia Intestinalis:
It lives in the large intestine of man causing diarrhea. Transmission takes place by tetranucleated cyst with contaminated food and water.
v.. Isopora Hominis:
It lives in the large intestine. Some other species occur in dogs and cats. They cause diarrhea and abdominal discomforts. Infection occurs by occysts through contamination.
vi. Sarocystis:
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It occurs in the muscles of oesophagus of sheep causing weakness of muscles. Transmission by cysts.
vii. Nosema Apis:
It occurs in the intestine and Malpighian tubules of honey bee causing Nosemia.
viii. Balantidium Coil:
It lives in the colon of man causing chronic ciliary dysentery. Transmission is by infective cysts.
ix. Eimeria:
It is found in the digestive tract of sheep, birds and cattle. It causes diarrhea to haemorrhage. Transmission by oocysts.
x. Trichomonas Gallinae:
It is found in the epithelial lining of oesophagus and crops of fowl, pigeons and turkeys. It causes necrotic nodules. Transmission through droppings.
xi. Histomonas Meleagridis:
It lives in the calcium and liver of turkeys and fowls causing black-head disease. Transmission by ingesting contaminated eggs of caecal worms.
Parasites of Blood and Lymph:
(i) Trypanosoma Sps:
A number of species of Trypanosoma are parasitic in the blood of man and other vertebrates.
These are:
(a) T. Gambiense:
It occur in the blood of man causing African sleeping sickness. It is transmitted through the bite of tsetse fly, Glossina palpalis.
(b) T. Rhodesiense:
In man it causes Rhodesian sleeping sickness. It is transmitted through the bite of tsetse fly, Glossina morsitans.
(c) T. Cruzi:
In early stage it is found in the muscles, heart, brain, special cord and in later stages in the blood. It causes Chaga’s disease in South and Central Africa. Infection transmitted by the bite of bug, Tritoma magista.
(d) T. Brucei:
It causes nagana disease in domesticated cattle’s and it is transmitted by Glossina morsitans.
(e) T. Evensi:
It occurs in the blood of horse dogs, camels etc. It causes surra disease. It is transmitted by Tabanus fly.
(f) T. Equiperdum:
It is found in the blood and germinal epithelium of houses, dogs and donkeys. It causes dourine disease in horse. The disease is transmitted during copulation.
(ii) Leishmania Sps:
It is a parasite of man and other animals.
A number of species are there:
(a) Leishmania Donovani:
It is found in the endothelial cells of blood and lymph capillaries and leucocytes in the spleen, liver, bone marrow and lymph gland causing visceral leishmaniasis or kala-azar. Infection occurs by the bite of sand-fly, Phlebotomus.
(b) L. Tropica:
It occurs in the endothelial cells of dermal tissues causing Oriental sore or cutaneous leishmaniasis in man. Infection occurs by the sand-fly.
(c) L Infentum:
It occurs in the spleen of children. It causes enlargement of spleen. Transmission by the bite of sand-fly.
(iii) Plasmodium Sps:
A number of species of Plasmodium occur as intracellular parasites in red blood corpuscles of man and birds. The Anopheles female is the vector.
These are:
(a) Plasmodium Vivex:
It causes benign terrain malaria.
(b) P. Ovale:
It also causes benign terrain malaria.
(c) P. Falciparum:
It causes malignant tertian.
(d) P. Malariae:
It causes quartan fever.
(e) P. Praecox:
It causes malaria in birds.
(f) P. Gallinaceum:
It causes malaria in chickens and pheasants.
(iv) Babesia Sps:
Three species of Babesia found in cattle’s, dogs and horse.
These are:
(a) Babesia Bigemina:
It occurs in R.B.C. of cattle’s causing Texas or Red water fever. It is transmitted by the bite of tick Boophilus.
(b) B. Canis:
It occurs in the R.B.Cs. of horses causing jaundice and sometimes paralysis of hind-limbs. Transmission through the ticks.
(c) Haemoproteus:
It is found in the R.B.Cs. and endothelial cells of blood vessels in birds.
Parasites of Urogenital Tract:
(i) Trichomonas Vaginalis:
It is found in the vagina of female causing vaginitis (annoying itch and abnormal discharge) and in man it is found in urethra. Transmission is direct through inter-course.
(ii) Trichomonas Foetus:
It occurs in the urogenital system of sheep, horse and cattle’s. It causes uterine and penial disorders. Transmission is direct through intercourse.
(iii) Eimeria Truncate:
It occurs in the kidneys of goose and often causes death of the host.