Pneumonic Plague

Plague

Plague is a zoonotic disease circulating mainly among small animals and their fleas. The bacteria Yersinia pestis can also infect humans. It is transmitted between animals and humans through the bite of infected fleas, direct contact, inhalation, and rarely, ingestion of infective materials. Plague can be very severe disease in the population, with a fatality rate of 30% -60% if untreated.

Infected persons usually start with "flu" symptoms after an incubation period of 3-7 days. Patients typically experience the sudden onset of fever, chills, head and body aches and weakness, vomiting and nausea. Clinical plague infection manifests itself in three forms depending on the route of infection: bubonic, septicemic, and pulmonary.

• Bubonic form is t he most common form of plague resulting from the bite of infected fleas. Plague bacillus enters the skin site of the bite and travels through the lymphatic system closest to the lymph nodes. The lymph node then becomes inflamed because of the plague bacteria, Yersinia pestis and Y. pestis, is here reproduced in large numbers. Swollen lymph nodes is called a "bubo" which is very painful and can become suppurated as an open wound at an advanced stage of infection;

• shape of the septicemic plague occurs when infection spreads directly into the bloodstream without evidence of a "bubo". More commonly, an advanced stage of the bubonic plague will result in the presence of Y. pestis in the blood. Septicemic plague May result from flea bites and direct contact with infectious materials through cracks in the skin.

• form of pneumonic plague is the more and less virulent form of plague. Typically, the pulmonary form is due to secondary spread from advanced infection of an initial bubonic form. Primary pneumonic plague results from inhalation of infectious aerosol droplets and can be transmitted from human to human without involvement of fleas or animals. The absence of treatment, pneumonic plague has a very high fatality rate.

Plague is endemic in many countries in Africa, former Soviet Union, the Americas and Asia. In 2003, 9 countries reported 2118 cases and 182 deaths. 98.7% of these cases and 98.9% of these deaths were reported from Africa. Today, the distribution of plague coincides with the geographical distribution of its natural homes.

Treatment
The diagnosis and prompt treatment is essential to reduce complications and deaths. Effective treatment methods enable almost all plague patients to be cured if diagnosed in time. These methods include the administration of antibiotics and support.

Prevention
The goal of prevention is to educate people to be aware of areas where zoonotic plague is active and to take precautions against flea bites and handling of carcasses in areas of endemic plague. People should avoid direct contact with infective tissues, or be exposed to patients with pneumonic plague.

The recognition of cases, medical and field investigations

• Identify the most likely source of infection in the area where the human case (s) have been described in general research areas grouped a large number of small animal die-offs. Institute for sanitation and control measures to stop the source of exposure;
• To disseminate information concerning the areas of active transmission of the plague, the clinical features of plague and the case definition for health workers;
• Check that patients have been placed on appropriate antibiotic treatment and that the local supply of antibiotics are adequate to handle new cases;
• Isolate pneumonic plague patients;
• Obtain samples for laboratory confirmation.

Laboratory tests
The diagnosis and confirmation of plague requires laboratory tests. The recovery and identification of the culture of Y. pestis from a patient sample is optimum for confirmation. Depending on the presentation of the form to the plague: bubo aspiration, blood and sputum samples are the most suitable for rapid testing and culture. Serum taken early and late stages of infection can be examined to confirm infection. Rapid dipstick tests have been validated for field use to quickly screen for antigens of Y. pestis in patients. The samples must be collected and sent to laboratories for plague testing.

Vaccination

Plague vaccines at the same time have been widely used but have not proved to be an approach that could effectively prevent the plague. The vaccines are not recommended for immediate protection in outbreak situations. Vaccination is only recommended as a prophylactic measure for high-risk groups (eg, laboratory personnel who are constantly at risk of contamination).

Surveillance and control

• Conduct investigation to identify animals and flea species that are implicated in the plague enzootic cycle in the region and develop a programme on environmental management to limit its potential spread.
• Active long-term surveillance of zoonotic foci and rapid response to reduce exposure during epizootic outbreaks have been successful in reducing human plague.