Contagious Caprine Pleuropneumonia

Introduction

Contagious caprine pleuropneumonia (CCPP) is a cause of major economic losses to goat producers in Africa and Asia.
This condition is caused by Mycoplasma capricolum subsp. capricolum and occasionally M. mycoides subsp. capri or M. mycoides subsp. mycoides. It is a member of the Mycoplasma mycoides cluster.
CCPP is characterized primarily by its contagious nature. The disease causes interstitial fibrinous pleuropneumonia, interlobular oedema and hepatization of the lung causing high mortality rates of up to 80% and morbidity rates of up to 100%.
The most important distinguishing features of CCPP, with respect to the other goat respiratory mycoplasmoses, were defined by Hutcheon and are quoted as follows:

1) The disease is readily contagious to all susceptible goats;

2) Sheep and cattle are not affected by disease;

3) Local oedematous reactions do not occur in goats when infective innoculum is given subcutaneously (Hutcheon, 1889).

Distribution

CCPP has been detected in at least 30 countries across Africa, the Middle East and Western Asia.
In natural infections, transmission of the disease is by aerosol.
The environment also plays an important role in the appearance, evolution and severity of CCPP. Due to the high sensitivity of mycoplasmas to the external environment, close contact is essential between infected and naive animals for transmission to take place, and overcrowding and confinement thus favours their circulation. Stress factors such as malnutrition and long transport can also predispose animals to disease. In Africa where extensive and traditional husbandry is practised, pathogens spread when animals meet at watering points and grazing areas.

Signalment

CCPP affects only goats, of any breed, sex or age worldwide. Younger animals tend to suffer more severe clinical signs than adults.

Clinical Signs

The animal may appear generally depressed, dull, weak and lethargic. The animal will then be pyrexic and have signs of weight loss of reduced weight gain.
If the animal is in milk then milk yield will be severely reduced. Sometimes the disease may manifest as sudden death only.
Respiratory signs include bilateral nasal discharge, dyspnoea, tachypnoea and coughing. Some goats may appear to be in severe respiratory distress.

Pathology

The gross pathological lesions are localized exclusively to lung and pleura and are often unilateral. Affected lungs can be totally hepatized, and have a port wine colour. A lung section shows a fine granular texture with various colours, but usually without any thickening of the interlobular septa.
Abundant pleural exudate and pleuritis are common. The pleural exudates may have solidified forming a gelatinous covering.
In acute cases, the pleural cavity contains an excess of straw-coloured fluid with fibrin flocculations . In chronic cases there is a black discolouration of the lung tissue and sequestration of necrotic lung areas.
Adhesions between the lung and the pleura are very common and often very thick
Histological examination of the lung tissues may show acute serofibrinous to chronic fibrino-necrotic pleuropneumonia with neutrophilic inflammation in the alveoli, bronchioles, interstitial septae and subpleural connective tissue. Intralobular oedema is prominent and local lymphoid hyperplasia common.

Diagnosis

High mortality and typical early thoracic lesions in goats are highly indicative of M. capricolum subsp. capripneumoniae infection, but are not diagnostic.
A valuable 'in the field' diagnostic procedure is the latex agglutination test(LAT). The long shelf-life of the beads at different temperatures makes it possible to prepare large amounts which can be stored until used. This combined with the rapidity of the test, being run in two minutes, makes it a practical and useful test.
Definitive diagnosis can also be made by the isolation of M. capricolum subsp. capripneumoniae from clinical samples, usually lung tissue but may be a long and difficult process and requires attentive sampling techniques.
The growth inhibition (GI) test is the simplest and most specific, but the least sensitive of the tests available.
The direct and indirect fluorescent antibody tests are among the most effective, simple and rapid serological methods of identification for most mycoplasmas.
The complement fixation test (CFT) and the indirect haemagglutination test (IHA) are serological methods of diagnosis, as is the ELISA. These have varying degrees of efficacy.
Diagnostic systems based on PCR have now been developed for the rapid detection, identification and differentiation of M. capricolum subsp. capripneumoniae.
The diagnosis of outbreaks of CCPP is often complicated by other infectious agents causing similar syndromes including other mycoplasmas and Pasteurella haemolytica.

Treatment and Control

The macrolides (erythromycin, spiramysin, and tylosin), tetracyclines and quinolones are active against M. capricolum subsp. capripneumoniae.
Control measures include prevention of mixing and good hygiene. Movement restrictions and slaughtering infected animals are recommended for countries that are newly infected.

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References

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