COMMON DISEASES IN POULTRY The common diseases and disorders of free-range poultry may be either infectious or non-infectious, and are caused by a wide range of organisms or deficiencies. These are summarised in Table 6.2. Disease control is discussed in a later section of this chapter. Table 6.2 Causes and examples of poultry diseases Causal Agent Example Infectious Virus Newcastle Disease, Avian Encephalomyelitis, Fowl Pox, Mareks Disease, Infectious Bronchitis Infectious Laryngotracheitis, Gumboro Disease (Infectious Bursal Disease), Duck Virus Hepatitis Mycoplasma Chronic Respiratory Disease Bacteria Fowl Cholera, Salmonellosis, Pullorum, Fowl Typhoid, Infectious Sinusitis, Colibacilosis Parasites Ectoparasites: lice, mites, ticks Endoparasites: nematodes, Histomoniasis, Haemoparasites, round worms, hair worms, Avian Malaria Protozoa: Coccidiosis, Blackhead Fungus Aspergillosis: A. flavis (toxins), A. fumigatus (airsaculitis) Non-Infectious Deficiencies rickets, curled toe paralysis, encephalomalacia Toxicities salt poisoning, food poisoning (Botulism Clostridium botulinum and C. perfringens), poisonous plants INFECTIOUS DISEASES Viral diseases Viral diseases are some of the most important infectious diseases affecting poultry. They are characterised by not being able to be treated, but most can be prevented with vaccines. The more important viral diseases are outlined below. Newcastle Disease (ND) This disease (called Ranikhet Disease in Asia) spreads rapidly via airborne droplets spread by the coughing or sneezing of infected birds. The virus can be carried by wild birds, through contaminated eggs, and on clothing. As mortality is often 100 percent in young chickens, ND is probably the most important constraint to family poultry development. Birds of any age can be affected, although young ones are more susceptible. Mortality in older chickens is usually lower, but egg production is usually severely reduced. The incubation period of three to five days is followed by dullness, coughing, sneezing and gasping. Rapid breathing is accompanied by a gurgling noise in the throat. The respiratory signs usually develop first and are sometimes followed by nervous signs, characterized by twisting of the neck, sometimes combined with dragging of wings and legs. Depending on the environment and the degree of resistance of the birds, not all symptoms may be shown, or they may be in a mild or subclinical form. Some farmers have observed that the twisting of the neck occurs only in birds that survive. Early loss of appetite results in a greenish diarrhoea. The most obvious diagnostic sign of ND is very sudden, very high mortality, often with few symptoms having had time to develop. Diagnosis of ND can be difficult from just the symptoms, as they are so varied, and as many other diseases share the same symptoms. For a discussion on the control of ND, see the “ND Control” section below. The high incidence of ND among family free-range flocks is due to the following factors: the prevalence of virulent strains (velogenic, viscerotropic and pneumotropic) in tropical countries; continuous contact with other domestic and wild species of birds (such as ducks and pigeons), which can carry the virus without showing the disease (Majiyagbe and Nawathe, 1981); and uncontrolled movement of birds between villages. READ MORE HERE vetprofession.net/2013/03/common-poultry-diseases-in-tanzaina.html
Posted on: Thu, 16 Oct 2014 14:05:34 +0000
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