Prevention of plague

In endemic areas, the control of plague in humans is based on the 2 main factors

• ·         Reduction of the likelihood of being bitten by infected fleas
• ·         Exposure to infected droplets from either humans or animals with plague pneumonia.

In the United States, residence and outdoor activity in rural areas of western states where epizootics occur are the main risk factors for infection.

How to assess the potential risk of plague to human in specific area?

To assess potential risks to humans in specific areas, surveillance for Y. pestis infection among animal plague hosts and vectors is carried out regularly as well as in response to observed animal die-offs.

What are the personal protective measures?

• Personal protective measures is very essential include avoidance of areas where a plague epizootic has been identified and publicized (e.g., by warning signs or closure of campsites).
• Sick or dead animals should not be handled by the general public.
• Hunters and zoologists should wear gloves when handling wild-animal carcasses in endemic areas.
• General measures to avoid rodent fleabite during outdoor activity are appropriate and include the use of insect repellant, insecticide, and protective clothing.
• General measures to reduce peridomestic and occupational human contact with rodents are advised and include rodent-proofing of buildings and food-waste stores and removal of potential rodent habitats (e.g., woodpiles and junk heaps).
• Flea control by insecticide treatment of wild rodents is an effective means of minimizing human contact with plague if an epizootic is identified in an area close to human habitation.
• Control of rodents-Any attempt to reduce rodent numbers must be preceded by flea suppression to reduce the migration of infected fleas to human hosts. An oral F1-V subunit vaccine using raccoon poxvirus (RCN) as a vector protects prairie dogs against Y. pestis injections and is being investigated for efficacy in preventing disease in wild animals, hence potentially reducing human exposure

Prevention of infection from suspected host

•  Patients in whom pneumonic plague is suspected should be managed in isolation, with droplet precautions taken  until pneumonia is excluded or effective antimicrobial therapy has been given for 48 h.
• The  main infective risk is posed by patients in the final stages of disease who are coughing up sputum with plentiful visible blood and/or pus.
• Cotton and gauze masks were protective in these circumstances.
•  Current surgical masks capable of barrier protection against droplets, including large respiratory particles, are considered protective; a particulate respirator (e.g., N95 or greater) is not required.

Antimicrobial Prophylaxis

 Postexposure antimicrobial prophylaxis for  7 days is recommended following household, hospital, or other close contact with persons with untreated pneumonic plague. (Close contact is defined as contact with a patient at <2 m.) In animal aerosolinfection studies, levofloxacin and ciprofloxacin are associated with higher survival rates than doxycycline

 Plague prevention by immunisation

Plague prevention - Immunisation against plague

Immunization studies with candidate plague vaccines in animal models show that neutralizing antibody provides protection against exposure but that cell-mediated immunity is so critical for protection and clearance of Y. pestis from the host.

There is 2 vaccine whole cell vaccine and live attenuated vaccine 

A killed whole-cell vaccine used in humans as many disadvantages

• Required multiple doses 
• Caused significant local and systemic reactions
• It failed to give protection against pneumonic plague

This vaccine is not currently available in the United States.

A live attenuated vaccine 

Live attenuated vaccine based on strain EV76 is still used in countries of the former Soviet Union but has significant side effects. Live attenuated vaccines closest to licensure are subunit vaccines comprising recombinant F1 (rF1) and various recombinant V (rV) proteins produced in Escherichia coli, that are combined either as a fusion protein or as a mixture, purified, and adsorbed to aluminum hydroxide for injection.

This combination will protects mice and various nonhuman primates in laboratory models of bubonic and pneumonic plague and has been evaluated in phase 2 clinical trials. Special ethical considerations with controlled clinical studies involving plague in humans make prelicensure field efficacy studies unlikely.

In the United States, the FDA is hence  prepared to assess plague vaccines for human use under the Animal Rule, using efficacy data and other results from animal studies as well as antibodies and other correlates of immunity from human vaccine recipients

Live attenuated Y. pseudotuberculosis and Salmonella strains expressing Y. pestis–specific antigens found to be  protective in laboratory animal models of bubonic and pneumonic type of plague and it can be also delivered by the oral route.

There is also a wide variety of other delivery mechanisms for Y. pestis antigens are being explored.

Antigens other than F1 and V that can be added to subunit vaccines are being investigated. Advances providing impetus for exploration of these antigens are the following

• The recovery of F1-negative Y. pestis strains from natural sources 
• The observation that F1 antigen is not required for virulence in primate models of pneumonic plague

Read ... Prevention of plague

Clinical manifestations of Infective Endocarditis

Fever is the most common manifestation of Infective Endocarditis (IE).

Heart murmurs are seen in 80 - 85% of cases

Enlargement of spleen is seen in 15 - 50% of cases.

Peripheral manifestations of IE are 

1. Petechiae is the most common peripheral sign

Palpebral conjunctiva, the buccal and palatal mucosa, and the extremities are the common sites of Petechiae

2. Splinter Hemorrhages

It is nonspecific and nonblanching 

Appear as linear reddish-brown lesions found under the nail bed

Usually do not extend the entire length of the nail

3. Osler’s Nodes

More specific for IE

Painful and erythematous nodules

Located on pulp of fingers and toes

More common in subacute IE

4 P’s related to oslers nodes are

Pink

Painful

Pea-sized 

Pulp of the fingers/toes

4. Janeway Lesions

More specific

Erythematous, blanching macules 

Nonpainful

Located on palms and soles

Myalgia, arthralgia, back pain can be present in IE patients

Systemic embolisation manifest as neurological and renal involvement 

Neurological manifestations are embolic stroke (most common) and mycotic aneurysm.

Renal insufficiency, immune-complex mediated glomerulonephritis  embolic renal infarct can occur in IE.