Pathogenecity

PATHOGENECITY
  • In avian species aspergillosis encountered in two main forms

Acute Aspergillosis

  • In which there is high morbidity and mortality in very young chicks.
  • This form of the disease is commonly known as brooder pneumonia.
  • Typical symptoms are loss of appetite, high temperature, listlessness, foetid diarrhoea, convulsion and affected chicks die with in 24-48hrs of the onset of symptoms.

Chronic Aspergillosis

  • It is seen in individual adult birds or few birds in a flock.
  • The affected birds may survive for longer periods in a gradually declining state.
  • Symptoms are very mild and it is associated with anaemia, yellowing of faeces and the presence of respiratory rattle.

Cattle

  • Conditions of high humidity and temperature encourage the growth of molds when hay and straw is stored and this constitutes the source of infection for cattle.
  • Aspergillus fumigatus is considered as the primary cause of mycotic abortion, however many other Aspergillus species, A.flavus, A.nidulans, A.niger, A.terreus and A.versicolor are also found to be associated with abortion.
  • Infections mainly occur by inhalation into lungs or by ingestion, and then carried to the placenta in the blood stream from lesions in the respiratory tract or ulcers, mycotic ruminits or other lesions of the digestive tract.
  • This results in a slowly developing fungal placentitis (one to two months) and intefere with the nutrition of the foetus, resulting in foetal death and abortion.
  • Chronic form may lead to purulent vaginitis, cervicitis and endometritis, resulting in infertility.
  • Abortion most commonly occurs in 6-7 months of gestation.
  • The aborted foetus shows discrete, raised ringworm type lesions on the skin of head and neck.
  • The placenta is found thickened, haemorrhagic, odematous and necrotic.
  • The cotyledons will be grey in color, inter cotyledonary area will be leathery, grey and tan in color.
  • On necropsy grayish or yellowish gaseous exudates with mycelia are commonly seen in the lung and airsac.
  • Sometimes the organism colonise the bronchi, forming a compact spherical colony, which is called fungus ball.
  • The fungal balls are produced most frequently by A.niger than A.fumigatus.
  • Characteristic nodular lesions are also seen in alimentary canal, kidneys and ovaries.
Last modified: Monday, 4 June 2012, 6:32 AM