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The term parasitology means the study of parasites, their hosts and the relationships between the parasite and its host. This is a subject which includes the living system, spread, dependency on the host etc of the particular parasite. Study of parasites is often broken into more focused topics.
Parasites depending upon their hosts can be again divided into so many types. Some of the parasites they make humans as their hosts to survive and we can find more than
300 species of parasitic worms and more than 70 species of protozoa. These parasites are found to be with us as an ancestral property that came from our primate ancestors and some of them can be infected to us through the domestic animals we keep at homes or come into contact with.
The term parasitology again can be divided in to many branches which include most important topics like medical parasitology, veterinary parasitology, structural parasitology, quantitative parasitology, parasite ecology, conservation biology of parasites and so on...
The term medical parasitology (to check microbiology parasitology samples on microbiology samples) is one of the biggest field of parasitology which deals with the parasites that infect human kind, the diseases caused by them, clinical picture and response generated by human diagnosis, treatment and their prevention and control methods.
Here are some of the parasites that effect human kind causing different diseases and some of the methods of diagnosis which can help for reference.
This is infective at the stage of egg through oral route. This needs no vector to carry and this directly damages colonic tissues. This can be diagnosed at the egg stage itself and diagnosis can be done through the test of stool.
2. ASCARIS LUMBRICOIDES:
This is also infective at the egg stage and infection occurs through oral route only. Disease symptoms are found when the worm grows into adult worm and migrates to aberrant sites in the body like Pancreas, liver, peritoneal cavity etc and intestinal blockage caused by the worm bolus in heavy infections. This can cause transitory pneumonia when the larva migrates to 3rd stage and trauma can be experienced due to migration of adult worms and secondary scepticemia also can be seen. This can be diagnosed in egg stage and can be determined through stool examination.
3. STRONGYLOIDES STERCORALIS:
This parasite is found in dogs and monkeys using them as their reservoir hosts. This can infect a human body at the third stage of larva when it is in soil. This parasite directly penetrates through skin by larva and rarely it can be infected orally also. If the patients are having less immunity then autoinfection can also be seen in some of the cases. The adults and larvae penetrate the villus tissue and bacteria enter into the tissues by the migrating larvae. Acute diarrhea in patients with lesser immunity is seen to a large extent and bacteria often lead to death in those patients. Diagnose can be done when the larva is in its habditiform that means its second stage. Diagnosis can be done by testing the stool of the patient and duodenal aspirate or string test.
4. SCHISTOMA MANSONI:
Another microbial parasite which infects the human body at Cercaria stage. This directly penetrates the human skin and this is carried by the intermediate hosts like aquatic fresh water snails. They act as intermediate host for these parasites. After the infection the eggs block the pre-sinusoidal capillaries in liver and blockage of lung capillaries also seen. Major disease symptoms are like portal-hypertension, cor pulmonale, esophageal varices and hypersplenism. This can be diagnosed at egg stage and method of diagnosis is stool examination or rectal snip.
5. SCHISTOMA HAEMATOBIUM:
Another parasite which again infects the human body at Cercaria stage which again penetrates through unbroken skin of the human being. Aquatic fresh water snails act as the intermediate host for this parasite which carries the parasite from one body to the other. These parasites use the primates as their reservoir hosts. Disease can be determined based on the symptoms like portal hypertension, esophageal varices, cor pulmonale, bladder ca, clacification of bladder with attendant damage to kidneys etc. The parasite eggs block the pre-sinusoidal capillaries of liver, block the capillaries of the lungs and eggs also my include squamous cell epthelioma. Diagnosis can be done at the stage of eggs and can be known by microscopical examination of urine.
6. Schistosoma Japonicum :
Schistosoma Japonicum is a human parasite which again infects in the cercaria stage through direct penetration in to unbroken skin. This needs no vector and aquatic fresh water snails act as the intermediate host for the parasite to spread from one to another. This uses dogs, monkeys, pigs and cattle as its reservoir host. Schistosoma japonicum eggs block the pre-sinusoidal capillaries in liver as well as capillaries in lungs and rarely they can also block the capillaries of CNS. This causes portal hypertension, esophageal varices, cor pulmonale, and hypersplenism is also one of the symptoms. Diagnosis can be done at the egg stage and can be found by examining the stool of the patient.
7. Taenia Saginata :
Taenia Saginata is one of the parasites that infects the human body in cystcercus in tissue of intermediate host that infects through oral intake of infected things or mud that present in unclean nails or hands. Cattle act as the intermediate host for the parasite and they need no reservoir host. This can be diagnosed at egg stage and can be diagnosed by India Ink injected into the gravid proglottid in to the 12 or more branches of uterus. Eggas also can be tested by clear stick test and rarely can be found by testing the stool of the infected patient.
8. Tenia Solium :
Tenia solium is seen infected to the human body in cysticerus stage in tissues by oral route. Intermediate host of Tenia Solium is pig. This can be diagnosed at the egg stage which can be diagnised by inject gravid proglottid with India ink and counts lateral branches to uterus also. Eggs can be found rarely in stool examination.
9. Larval infection with Tenia Solium :
This infects to the host in egg condition through oral route. Intermediate host of the parasite is pig and human being itself and requires no reservoir host for survival. When the infection happens in the host that experiences neurological disturbances related to space occupying lesions which is caused due to the migration of hexacanth larva to different areas of the body and encysts forming a small space occupying lesion. This causes Cysticercus in tissues and can be diagnosed through direct biopsy and indirectly serological test looking for arc 5 through Immunoelectrophoresis.
10.Echinococcus Granulosus :
Disease called hydatid disease caused due to larval infection of Echinococcus Granulosis to human body through oral route. Herbivores and human beings themselves act as intermediate host for the parasite and pathalogy basis being the hexacanth larvae migrate to various areas of the body and develop in to large space occupying lesions which are called as hydatid cysts. Consequesnces of the disease are the obstructions or replacements of tissues by the hydatis cysts and anaphylaxis due to rupturing of cyst by the parasite. Disease can be diagnosed at the Protoscolices stage or hooklets can also be called as hydatid sand and this can be diagnosed through direct biopsy which is contra indicated and indirectly tested by Serology and look for arc 5.
11. Diphyllobothrium Latum :
Diphyllobothrium Latum is a human parasite that infects the host in Plerocerus stage wich can be caused by raw or under cooked muscle of intermediate host through oral infection. Copepods is the 1st intermediate host, fresh water fish acts as the 2nd intermediate host for the parasite to spread the disease from one host to the other. Reservoir host for the parasite are bear and dog. The adult wrms accumulate vitamin B12 which causes megalobastic anemia in the host. This can be found in egg condition and can be examined in the stool of the infected patient.
12. Plasmodium Vivax, Ovale, and Malariae :
The route cause of Malaria in the human body which is caused by mosquito bite through the Sporozite of the Plasmodium Vivax, Ovale and Malariae parasites subsequently causes fever, chills, anemia, splenomegaly and many more complications in the infected hosts. This is infected in to the human body through skin through mosquito bite which introduces the sporozites which transfusions through out the body and sometimes it can be congenital also. Female anophelis mosquito acts as the vector for the parasite and intermediate host being human body. The parasite destructs the RBC present in the blood directly or indirectly which causes the disease. This causes the infecton at the stage of Asexual and sexual stages of parasites in RBC's which can be examined through direct thin and thick blood films stained with Giemsa and indirectly by serological tests also.
13. Plasmodium Faciparum:
Disease called brain fever commonly seen in unclean plces dwelings frequently is caused by Plasmodium Falciparum which is injected in to the human body through mosquito bite at Sporozite stage of the parasite. This is also infected through blood transfusion and sometimes can be congenital. Vector being female anophelis mosquito and human body acts as the intermediate host for the parasite. These parasit sporozites cause anoxia by blocking capillaries in brain which results in fever, chill, anemia, splenomegaly, coma and death also seen in cases. Asexual and sexual stages of parasites in RBCs are the diagnostic stage of the parasite and can be examined in thick and thin blood films stained with Giemsa and indirectly by serology. The parasite destroys the RBCs directly or indrectly when infected into the blood through mosquito bite.
14. Toxoplasma Gondii :
Toxoplasma Gondii is a parasite which infects at the stage of Pseudocysts present in infected meat and oocysts in cat feces. This is caused by oral infection to the human body which includes the intermediate hosts man, other mammals and avians. All warm-blooded animals acts as reservoir host for the parasite. The parasite invades virtually all cell types in body and damages the immunological competence of the host depending on the severity. Infecton impairs lymphatic involvement which also resembles mononucleosis. This can be diagnosed by the demonstration of pseudocysts containing rophozoites in biopsed material which can be examined by biopsy or indirectly tested by serology method also.
15. Giardia Lamblia :
Giardia Lamblia infects the human body while the cyst stage through oral intake by infected hands and so. Beaver and dog act as reservoir host for the parasite whose Trophozoites attach to intestinal mucosa and cause flattening of villi. This results in malabsorption syndrome, cramping diarrhea, weight loss etc which can be examined through testing stool, duodenal aspirate and string test of the patient.
16. Entamoeda Histolytica :
Entamoeba Histolytica is a parasite infects in cystic condition through oral infection. Infection causes lesions and ulcerations inside the intestinal mucosa, abscesses of liver and brain due to the secretion of cytotoxic and cytolytic enzymes by the trophozites of the parasite. This results in Diarrhea, dysentry, space-occupying lesions and can ocassionally lead to the death of the host. This can be diagnosed at cyst and trophozoite stage of the parasite which can be found through stool examinations and indirectly found by testing in serology method.