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Zoonoses

What are Zoonoses?

 

Essentially zoonoses are infectious diseases which usually affect other animals, but which can also afflict humans. Zoonoses can be contracted through occupational exposure, or other environmental exposure. This page illustrates some diseases of this kind, and closely related ones. 

Anthrax
Erysipeloid
Orf
Trypanosomiasis
Ovine Chlamydiosis
 

This page is being revised. Amongst others, a section on Brucellosis is intended.

Anthrax

Anthrax is now a very rare disease. In an               occupational context it has been contracted from    exposure to biological materials from ruminant           animals such as skin/hide/wool, bone etc. The    disease can be contracted through the skin          (cutaneous), lungs (pulmonary), or gastrointestinal     routes. The image alongside (courtesy of Prof RI      McCallum) shows the commonest occupational        presentation of the disease - cutaneous anthrax. In    this case it was probably contracted from exposure   to bones from ruminant animals. This type of lesio has been called a 'malignant pustule' but this is a      misnomer since it is neither pustular (it is a hard  eschar which oozes serosanguinous material) nor is
 it malignant in the pathological sense. The         appearance of the skin lesion gives the name to the    disease since it had been likened to a piece of coal    (Greek: anthracos).  

                                 Anthrax is caused by a Gram+ rod-like bacterium called Bacillus anthracis. The spores of this organism are amongst the hardiest pathogenic spores in terms of the length of their survival and their resistance to destruction either within the animal product or in the soil. When man is infected the bacterium multiplies and generates a toxin.  

                                 The cutaneous form of the disease has the best prognosis of the three types, especially if recognised and treated early with appropriate antibiotics. The pulmonary form tended as had been contracted by woolsorters tended to be fatal as a result of a severe pneumonitis as well as sytemic effects. Most manifestations of the disease  feature a necrotising lymphadenitis.                               
                                                                                
 

                                                                               
 

Erysipeloid

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Trypanosomiasis

Thankfully this is a very rare condition in the UK, with perhaps to the order of only one new case per year. However it can present in tourists returning from parts of Africa where it is endemic.		 Trypanosomes in human blood

Orf

  
Orf is a viral infection of sheep, goats and cattle. It is said to be the Anglo Saxon word for 'cattle'. 

It is caused by a pox virus and produces a pustular dermatitis in the beasts. It can be occupationally contracted by humans, say a vet or a farmer might catch it from a sheep, but it might be contracted say by handling sheep's heads, so conceivably meat packers could catch it. It causes a skin lesion in man which is usually not serious and resolves spontaneously.

 The image for this is in preparation
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Ovine Chlamydiosis

  
Sheep in the lambing season, may shed Chlamydiae with their afterbirth in particular, and these organisms can be responsible for abortion in humans. What may appear to be a fairly safe and idyllic rural acticvity might in fact therefore present a significant risk to human reproductive health. Other organisms which may cause serious health hazards to pregnant women in the lambing season include Listeria and Toxoplasma. Read more about hazards of farming.