(a) Discuss anthrax disease under the following headings: causative organisms two modes of transmission; (b) Draw and label the reproductive tract of a hen....

(a) Anthrax disease

Causative organism:

Anthrax is caused by the bacterium Bacillus anthracis, a large, rod-shaped, spore-forming bacterium. Its spores are extremely resistant and can survive in the soil for many years.

Two modes of transmission:

1. Ingestion of contaminated feed and water - animals swallow anthrax spores while grazing on pasture, or feeding and drinking from feeders, drinkers or water sources contaminated with the spores.
2. Through open wounds or body contact - spores enter the body through cuts, wounds or abrasions on the skin; the disease can also be spread mechanically by biting flies and other vectors, or by inhalation of spores.

(b) The reproductive tract of a hen

The domestic hen has a single functional reproductive system on the left side of the body (the right ovary and oviduct remain undeveloped). The tract consists of an ovary bearing a cluster of developing ova (yolks) and a long, coiled oviduct made up of the infundibulum, magnum, isthmus, uterus (shell gland) and vagina, which opens into the cloaca (vent).

As the yolk (ovum) is released from the ovary it is caught by the infundibulum, then passes through the magnum (where thick albumen/egg white is added), the isthmus (where the shell membranes are formed), the uterus or shell gland (where the hard calcareous shell and shell pigment are deposited), and finally through the vagina and out through the cloaca (vent) as a fully formed egg.