Some Swine Reportable and Zoonotic diseases

 

Anthrax

 

Cancer swollen neck 2

Anthrax is caused by the bacterium Bacillus anthracis.  When this bacteria infects a pig there may be very few clinical signs, but occasionally the bacteria results in an acute illness, fever, respiratory distress and sudden death.

Anthrax should be suspected in any pig found suddenly dead with a swollen neck with copious blood tinged mucus and large haemorrhagic lymph-nodes.  

Pig with a swollen neck

When suspicious, make an incision into the swollen neck region and take some of the lymph fluid.  Do not fix the slide with heat, allow to air dry.  Bacillus anthracis does not form the characteristic capsule readily in pigs and the capsule that does form is broken down with heat.   If the suspicions are confirmed, stop the post-mortem and inform a government veterinarian.  In pigs the spleen is not enlarged as in cattle. 

 

Take great care with diseases animals and the carcase as anthrax is zoonotic.

 

The source of B. anthracis is normally through contaminated feed.  Outdoor sows may contract spores through the soil or contact with carcasses.

 

Rabies

Rabies is caused by a Rhabdovirus.  The disease is rare in pigs.  Pigs however, like all mammals may become infected if bitten by an affected animal – for instance a Raccoon in the USA.

Following an extremely variable incubation period, sometimes over 100 days, the pig suddenly develops clinical signs of in coordination and dullness which within days progresses to prostration and death.   Diagnosis can be problematic as post-mortem lesions may be non-descript.  If suspicious submit the whole carcase to a diagnostic laboratory.   There is no treatment.  Control is via good biosecurity, limiting pigs’ access to other wild mammals.  This can be impossible in outdoor or pasture pigs.  Pet pigs may be vaccinated every three years using a standard canine rabies vaccine, but note the vaccine is not licensed or proven on pigs.

 

 

 

 

 

Tuberculosis

 

TB Neck Lymphnodes

Pigs are susceptible to Mycobacterium tuberculosis, M. bovis and M. avian/intracellulare complex.  Majority of the cases are associated with M. avian/intracellulare complex resulting in nodules in the lymph nodes of the neck and small intestine.  

Swollen neck lymph node with nodules

 

This may result in head and possibly the whole carcase if the case is more progressive.  Many of these TB nodules actually reveal Rhodococcus equi rather than mycobacterium.  There are no clinical signs in the pig. 

 

The source of the infection can include:

Outdoor pigs – badges and poultry manure

Sawdust and shavings

Peat – particularly if unpasturized when used in as piglet gut conditioners in the farrowing house

Water contamination

 

Infected pigs can be identified by routine TB testing.

 

Japanese B Encephalitis virus

 

Japanese B Encephalitis virus is common in South Asia. The virus belongs to the Flaviviridae family. The disease causes few problems in the pig, perhaps being associated with sporadic reproductive problems.   The significance of the disease is associated with public health.  The major clinical sign, when there are any, may include testicular degeneration and loss of fertility in the male and the birth of abnormal piglets with mummification.  The disease is spread by mosquitoes.

In areas where Japanese B Encephalitis virus is common, vaccination is possible prior to the mosquito season.  West Nile Virus is another Flaviviridae and it remains to be demonstrated if West Nile Virus is implicated in reproductive problems in pigs.

 

Enterovirus Encephalomyelitis

The clinical disease is called Teschen or Talfan and is associated with porcine enterovirus serotype 1.   The disease agent is extremely common and widespread.   The clinical signs are more common in weaned or growing pigs that develop an ascending paralysis particularly of the hind legs leading to a swaying gait and ultimately total paralysis.   Diagnosis can be confirmed by paired serology.  There is no effective treatment.  Control is by good introduction and acclimatization programmes, particularly of gilts and ensuring adequate colostrum intake of piglets.

 

Toxoplasmosis

Toxoplasmosis is caused by the protozoa Toxoplasma gondii.  This is a zoonotic disease.  Cats are the primary host.  Initially pigs become infected by ingesting feed or water contaminated by cat feaces. The pigs can then spread the parasite within a group by biting and vices, eating infected rodents and through feed back of placenta.  There are no real specific clinical signs in the pig.   The disease is significant from a meat hygiene aspect.

 

Typanosoma

Typanosoma simiae can cause an acute infection in the pig.  The pig develops very high fever, shivering and dies.  It should be considered as a major cause of death in high Tsete fly infested areas.

Differentiate from African Swine Fever – which generally kills many pigs at the same time and occurs in non tsete fly areas.  Blood smear will reveal T. simiae.  Typanosoma brucei may also cause mortality in pigs.

Pigs can act as a reservoir for T. rhodesiense or T. gambiense making pigs important in the spread of sleeping sickness. This is important given the close association with man and pigs.  Although pigs can also be positive in the control of Tsete flies as they cut down the thickets near African homesteads.

Pigs in Uganda roaming the villages and town – note rooting around the rubbish.

 

West Nile Virus

West Nile Virus is another Flaviviridae and it remains to be demonstrated if West Nile Virus is implicated in reproductive problems in pigs.