Although immunological and molecular techniques are being increasingly utilized for the diagnosis of parasitic diseases, conventional faecal and blood smear examinations remain the primary method employed by veterinary practitioners worldwide, based on the principle of "seeing is believing.Despite the advancements in technology, these techniques continue to be the gold standard and cost-effective means of diagnosing parasitic infections in domestic animals.
Diagnosis is an integral part of control strategies against parasitic diseases in domestic animals. Identification of parasites by microscopy is the basis for both diagnostics and epidemiological assessment of parasite burden of the host. Veterinary clinicians usually face difficulty in proper diagnosis of clinical and subclinical cases of parasitosis in farm animals, pets and poultry due to non availability of requisite information on commonly used diagnostic procedures at one place despite more than half of the cases reported in veterinary clinics and hospitals are of parasitic origin.
To identify parasitic infections, it is essential to examine excretory- secretory products (ESPs), viz., faeces, urine, sputum and nasal discharges as examination of such material is essential for clinical diagnosis. It is extremely rare to get an animal completely free from parasites and at the same time all animals may not show signs of disease. Most of the important helminths and coccidia inhabit intestinal tract. Therefore, clinical diagnosis of gut dwelling helminths and coccidian depends mostly on identification of ova/oocyst in faecal samples
Before proceeding to find out the nature of the egg content of the faecal sample, one should know what class of animal the faecal sample belongs to. It is easy to identify a faecal sample of herbivore from that of an omnivore or a carnivore. The dung of cattle, sheep and horse will contain lot of vegetable fibers. The colour of the dung under normal conditions will be dark greenish yellow with a peculiar aromatic smell. But the faeces of a dog or cat will be soft and pasty devoid of fibers and dark yellow in colour with an unpleasant smell. Several procedures commonly used to examine faeces for parasites are described in this section. Before attempting to apply these procedures, a few points should be considered:
Mange or parasitic dermatitis is caused by the infestation of mange mites e.g. Sarcoptes, Psoroptes, Demodex spp. and a range of other mites. The condition is characterized by itching and rubbing of the infested parts of the body against hard objects. Lesions include hair loss, dry, rough, thickened and wrinkled skin accompanied by the presence of scab and foul odour in some cases. Some mites burrow into the host epidermis (Sarcoptes) while others spend their entire life cycle on the skin surface (Psoroptes). Most mites are microscopic or less than 1mm in length; therefore skin scrapings are taken from the affected area of animals suspected to be suffering from mange or parasitic dermatitis
Collection of blood Blood sample should be collected in a capped clean and dry vial containing an appropriate amount of anticoagulant. The commonly used anticoagulants are ethylene diamine tetra acetic acid (EDTA) @ 1-2 mg/ml and heparin @ 5 I.U./ ml of blood. Sites for blood collection Before collection of blood clean the site of collection by applying some antiseptic solution. If the area is hairy shaving of the site under aseptic condition should be done. Tip of the ear should be preferred for prompt or early diagnosis of haemoprotozoan infections. The vein can then be punctured with hypodermic needle and the collected blood is transferred to a clean glass vial. For collection of blood various preferred sites in different animals are as under
HELMINTHS Collection of parasites Fresh helminth parasites should be collected, as far as possible to achieve better results in staining. This can best be done by conducting a post-mortem examination of the animal for which the procedure given below should be followed. On opening the body and before removal of the viscera, examine the body cavity (for free lying parasites, e.g. Setaria), subcutaneous tissue (for Parafilaria and Hypoderma larvae) and the surfaces of internal organs for spot or nodules that might contain parasites. Remove them for histopathological examination (in 10 % formalin). Remove the visceral organs separately and place them in different enamel trays.
Diagnosis of parasitic infections is routinely done with conventional parasitological techniques as described earlier. However, when the parasitaemia is too low to be detected by the conventional methods as in subclinical infections and/or carrier animals advanced diagnostic tools are used for the early, sensitive as well as specific diagnosis. Serological techniques Diagnostic techniques used mostly in laboratories needs various reagents and equipments to perform the test. However, a diagnostic kit is the extrapolation of the same method by packing it in a user friendly format, accompanied by all or most of the reagents required to perform the test and can also be done outside the lab or under field conditions. Various immunodiagnostic kits are available which are based on different diagnostic methods like Enzyme-linked immuno sorbent assay (ELISA). Complement fixation test (CFT), Agar gel immunodiffusion test (AGID), Immunofluorescent tests (IFT), Latex agglutination tests (LAT) etc. ELISA is the most commonly used test system and numerous kits based on ELISA are available commercially.
Chemotherapy in Parasitology deals with the treatment of disease caused by different parasites by specific drugs; meanwhile particular drug has got the particular action against the particular parasite. Recently chemotherapy is a extensively used and emerging branch for the control of different stages of parasites that is normally not killed by the conventional methods of treatment. Thus, chemotherapy plays an important role in the treatment and control of parasitic infections by avoiding the outcome of the danger of the disease by treatment of the affected animals. They should have the maximum parasitotrophic action and minimum organotrophic action. It is mainly divided into two types: 1) Rational therapy: It is a mode of treatment based on the pharmacological actions of drugs with relation to disease. 2) Supportive therapy: It is a method of treatment other than drugs, e.g. giving high protein diet in the oedematous condition such as bottle jaw in fascioliosis and amphistomiosis. The drugs used for the killing or complete removal of the parasites from the body of the host called antiparasitic drugs.
A. Evaluation of the efficacy and resistance of anthelmintics against Helminths Anthelmintic resistance According to WAAVP (World Association for the Advancement of Veterinary Parasitology) anthelmintic resistance is a failure to reduce feacal nematode egg count by at least 95%. Technically accurate definition is that resistance is a genetically determine decline in the efficacy of an anthelmintic against a population of parasite that is susceptible to the drug. The history of parasite resistance to anthelmintic starts with the first report on phenothiazine resistance in 1957. Haemonchus contortus was the first nematode to develop resistance against different anthelmintic. The World Association for the Advancement of Veterinary Parasitology has recommended two tests for detecting anthelmintic resistance in ruminants, horses and pigs. These are in vivo test (FECRT) and an in vitro test (the egg hatch test). Detection Technique
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