MIC 444 Agricultural Microbiology 34.pptx

Animal disease

1. FOWL CHOLERA It is a highly contagious bacterial disease of domestic and wild birds Etiological agent: Pasteurella multocida The organism is Gram negative, non-motile rod with a capsule It is susceptible to disinfectants, sunlight, drying and heat Susceptible birds: Turkeys and waterfowl are more susceptible than chickens Older chickens are more susceptible than young ones Some breeds of chickens are more susceptible than others

2. Fowl cholera cont’d Fowl cholera occurs as septicaemia of sudden onset with high morbidity and mortality Chronic and asymptomatic infections also occur Transmission Both asymptomatic carriers and chronically infected birds are the major source of infection P. multocida can be introduced into poultry flock by wild birds Transmission of the organism within a flock is through secretions from mouth, nose and conjunctiva of diseased birds that contaminate their environment and equipment such as crates, feed bags, shoes e.t.c . on which they survive for a long time

3. Symptoms Acute fowl cholera: Sudden death Protracted cases: Depression, anorexia Mucoid discharge from the mouth Ruffled feathers Diarrhoea Increased respiratory rate Chronic fowl cholera: Localized infections of the sternal bursae , wattles, joints, tendon sheats and foot pads which often get swollen There may be exudative conjunctivitis and pharyngitis

4. Diagnosis In addition to history, symptoms and lesions, P. multocida should be isolated , characterised and identified for confirmation Media for isolation: Blood agar, dextrose starch agar, typticase soy agar Enrichment with 5% heat-inactivated serum can be done Organism can be isolated from visceral of birds that died from peracute /acute fowl cholera PCR can be used for the detection of P. multocida in cultures and clinical samples

5. Prevention 1. Good management practices are essential for prevention 2. Rodents, wild birds, pets and other animals that may be carriers of P. multocida must be excluded from poultry houses 3. Attenuated live vaccines are administered by wing-web inoculation to healthy flocks only Treatment Sulphonamides and antibiotics in adequate dosage can be used for early treatment Sulfaquinoxaline sodium or sulfamethazine or sulfadimethoxine can be administered through feed and water Tetracycline administered in feed, drinking water or parenterally can be useful Norfloxacin in drinking water can be used

6. Treatment cont’d Penicillin is effective against sulfa -resistant infections Combination of streptomycin and dihydrostreptomycin is effective in ducks Although many drugs lower mortality from fowl cholera they do not eliminate P. multocida from the the flock. Death of the flocks may resume when treatment is discontinued Eradication of infection: Eradication of infection requires depopulation, cleaning and disinfection of buildings and equipment

7. AVIAN BOTULISM Botulism is an intoxication that results from ingestion of preformed exotoxin of Clostridium botulinum Etiological agent: Clostridium botulinum The organism is Gram positive, spore-forming rod It acts by blocking nerve function which leads to respiratory and musculoskeletal paralysis Illness is caused by the toxin produced by C. botulinum and not by the bacterium itself Several types of toxins are produced by the organism but type C and to a lesser extent type E affect birds The bacterium is widespread in the soil

8. Requirements for toxin production: Protein source e.g. decomposing insect Warm temperature Anaerobic environment Transmission: Birds either ingest toxin directly or may eat invertebrates e.g. fly larvae containing toxin L arvae or maggots feed on animal carcass and ingest toxin Note that larvae or maggots are not affected by the toxin stored in their body When ducks consume toxin-laden maggots they develop botulism even after ingesting as low as 3 or 4 maggots A transmission circle is thus generated

9. Susceptible birds: Fowl, turkey, waterfowl, and most wild birds Death from botulism is common in water fowl because they feed in stagnant water holes Domestic fowl raised under poor hygiene and where the birds have access to rotten carcass will be prone to botulism Ten to one hundred thousand birds die of botulism annually, in large outbreak a million or more birds may die Botulism in birds may be self limiting. On the other hand, mortality can be as high as 40% Symptoms Poultry and wild birds usually have flaccid paralysis in the legs, wings, neck (twisting) and eye lids Broiler chicken may also have diarrhoea and respiratory problems

10. Symptoms cont’d Due to paralysis, birds can not use their wings and legs or raise their eye lids They can not control their neck muscle or other muscle and so can not hold their heads up Death can occur from water deprivation, electrolyte imbalance, respiratory failure or predation Diagnosis Preliminary diagnosis is based on clinical signs Confirmatory diagnosis of botulism is based on demonstration of the toxin in serum from sick birds or tissue samples from freshly dead birds Samples of dead birds are unreliable because C. botulinum toxin can result from post-mortem multiplication of the organism and toxin production Molecular test based on ELISA can be used to detect C. botulinum toxin, genes responsible for toxin production and differentiate the different types of toxins

11. Diagnosis cont’d Botulinum toxins are heat labile and can be destroyed at 80 o C for ≥ 10 minutes So collected serum must be transported in ice packs to the laboratory Prevention 1. Dead birds should be disposed off properly 2. Fly control may reduce the risk of toxic maggots in the environment 3. Cleaning and disinfection around poultry houses 4. Active immunization with inactivated type C bacterin-toxoids. But it is not cost effective

12. Treatment 1. Affected birds may recover without treatment 2. Treatment with type-specific antitoxin is effective