Although immunological and molecular techniques are increasingly being applied for the diagnosis of parasitic diseases, veterinary practitioners worldwide still rely primarily on the conventional faecal and blood smear examinations mainly on the concept of "seeing is believing". These techniqes are still the gold standard and cost-effective means of diagnosing the parasitic infections in domestic animals.
Preface 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. Although various diagnostic techniques are amply available in textbooks and manuals, yet these procedures lie distributed in different compilations that are mostly available in libraries, thus not easily accessible to field diagnosticians. Therefore, an attempt has been made by the authors to compile easily adoptable diagnostic techniques for use of field veterinarians as well as students with the ultimate aim for substantial control of different types of parasitic infections and infestations in farm animals, pets and poultry. Although immunological and molecular techniques are increasingly being applied for the diagnosis of parasitic diseases, veterinary practitioners worldwide still rely primarily on the conventional faecal and blood smear examinations based on the concept of “seeing is believing”. These techniques are still the gold standard and cost-effective means of diagnosing the parasitic infections in domestic animals. Our sincere thanks are due to all the faculty members and postgraduate students of Department of Veterinary Parasitology for their facilitation in preparation of the book. Special thanks are due to (Late) Dr B S Gill, Ex-Dean, for his critical evaluation and invaluable inputs for improving the overall quality of the book. Any suggestions from the readers for improvement of this book will be highly appreciated.
For the laboratory diagnosis of the parasitic infections, it is essential to examine various excretory-secretory products, viz., faeces, urine 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. Since, most of the important helminths and coccidia inhabit intestinal tract, therefore, clinical diagnosis of gut dwelling helminths and coccidia depends mainly on identification of ova/oocyst in faecal samples.
Examination of faecal sample for helminthic infections Gross Examination: It precedes the microscopic examination of faecal sample and includes collection of information as below: a) Consistency: Condition of the faeces should be noted as soft, watery (diarrhoeic) or hard but it should be kept in mind that the description varies with the concerned animal species. b) Colour: It is to report the unusual faecal colour, if any as mud coloured foul smelling faeces in calves indicate ascarid infection; tarry coloured faeces in dog is pinpointing of hookworm infection.
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, 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.
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 postmortem 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 sized 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 need 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 laboratory or under field conditions.
Commonly used chemicals/glasswares/ equipments in diagnostic laboratory Equipments and glasswares Research microscope Centrifuge machine Baermann’s apparatus McMaster chamber Centrifuge tubes (15 ml) Glass slides Cover-slips Soft cloth (Muslin) Tissue paper Microscopic immersion oil Plastic bottles Brushes and needles Petri dishes Specimen tubes Pestle and mortar Strainer Scalpel Scissors Forceps Glass vials Staining Rack
