Malaria Prevention and Travel Vaccines Updates from CDC at Society Meeting

Special Report

By Lin Chen, MD

Assistant Clinical Professor, Harvard Medical School; Director, Travel Resource Center, Mt. Auburn Hospital, Cambridge, MA.

Dr. Chen reports no financial relationship relevant to this field of study.

At the 56th annual meeting of the American Society of Tropical Medicine and Hygiene held Nov. 4-8, 2007, in Philadelphia, Paul Arguin, MD, Chief of the Domestic Malaria Unit at the Centers for Disease Control and Prevention, presented the Malaria Prevention Update from the CDC. He covered the following topics: 1) preliminary data from 2006 malaria surveillance; 2) rapid diagnostic tests; 3) recent outbreaks (Jamaica, Bahamas); 4) malaria maps; 5) artesunate availability in the United States; 6) e-mail updates.

The preliminary data showed approximately 1,400 cases of malaria reported to the CDC in 2006. Of those, 60% occurred in U.S. civilians, 20% in foreign civilians, 6% in military personnel, and 14% were in persons of unknown category. Among the U.S. civilians, main species of malaria were Plasmodium falciparum and P. vivax (41.3% and 22.0%, respectively). Countries where the exposures occurred most frequently were Nigeria, India, Ghana, Afghanistan, Uganda, and Sierra Leone. Among the foreign visitors, the most common countries where patients acquired malaria were India, Nigeria, Ghana, and Cameroon. The most frequently cited reason for travel was VFR (47.1%). There were six deaths attributed to malaria: five cases of P. falciparum (acquired in Ghana, Nigeria, Kenya, Uganda), and one case of P. malariae (acquired in Thailand).

Dr. Arguin reported on the FDA approval of BinaxNOW Malaria, a rapid diagnostic test for malaria, which may become very useful in decreasing the time to diagnosis of malaria (see the October 2007 issue of TMA Updates for a review of BinaxNOW Malaria). He then discussed the recent malaria outbreaks in Jamaica and Bahamas. The first case of malaria in the United States associated with travel to Jamaica occurred in a 44-year-old woman VFR traveler, who had lived in New York for 12 years. She visited Jamaica from Oct. 29 to Nov. 6, 2006, and developed symptoms on Nov. 20, 2006. She was diagnosed with P. falciparum, and responded to chloroquine. This case was associated with an outbreak in Kingston from late 2006 to June 2007 that totaled 370 reported cases. It had appeared that the outbreak was over, but in October 2007, two new cases of malaria were diagnosed along with leptospirosis and dengue outbreaks. The CDC again recommended chloroquine for travelers visiting Kingston. The likely source is attributed to a traveler from Haiti.

The Bahamas also experienced two outbreaks of malaria on Great Exuma: one in 2006 and one in 2007. The first outbreak resulted in 19 cases reported from May to June 2006, including four cases occurring in travelers, which led to the recommendation for malaria chemoprophylaxis temporarily. In August 2007, the CDC received reports of malaria in an 18-year-old male traveler, who lived in Florida and had only traveled to the island of Great Exuma. The Bahamas authorities detected one additional case at that time. No new cases have occurred since then, and the CDC planned to rescind the recommendation for chloroquine in November 2007 (this recommendation has been posted as of Dec. 13, 2007).

The CDC has developed malaria maps as a geography tool, where queries on a location will draw up recommendations for malaria prevention for the location. This is being tested at www.cdc.gov/malaria/risk_map/.

Artesunate is now available to treat malaria. In the United States, there are 50-100 cases of severe malaria annually, and 54 deaths occurred from 1999-2006. The CDC is making artesunate available under an IND protocol, and inclusion criteria are: patient with malaria; parenteral medication is required; artesunate is preferred, either because it is more readily available than quinidine, the patient has failed quinidine, is not tolerating quinidine, or if both drugs are equally available and artesunate is preferred by the treating physician. Artesunate has been released by CDC for seven patients to date: average age is 35, range 2 to 58 years of age. Of those, 57% are male, 100% P. falciparum; 83% acquired in Africa and 17% in the Caribbean. Eighty percent received it because quinidine was not available, while 20% received it because quinidine was not being tolerated. Most of these cases of severe malaria were associated with significant delay in diagnosis [onset of symptoms to hospital presentation, 5.4 days (3-7)] which is a known risk factor for developing severe disease. The average time from the artesunate request to shipping has been 1 hour (range 0.4-10.8 hours), and the average length of time from the artesunate request to treatment has been 4.3 hours (range 3.5-15.5 hours). One of the patients who received artesunate was subsequently found not to have had malaria. All patients have survived. One patient had a severe adverse event. This patient developed acute renal failure. However, upon review, it was felt that the renal failure was caused by the severe malaria and was not due to artesunate. In summary, parenteral artesunate (IV) is available. The distribution system is working, and the drug is effective. However, thus far it is underutilized. The CDC anticipates request for the drug about once per week. Request the drug from 770-488-7788 during the day and 770-488-7100 after hours, weekends, and holidays.

Additionally, the malaria updates from the CDC are available via e-mail. To subscribe to the free service, go to www.cdc.gov/malaria/ and follow the link on the right side of the screen: "Get e-mail updates."

Nina Marano, DVM, MPH, Branch Chief Geographic Medicine and Health Promotion Branch, CDC, presented the CDC Travel Vaccines Updates. The Advisory Committee on Immunization Practices (ACIP) recently recommended hepatitis A vaccine over the single dose of IG for healthy travelers with imminent departure.1

In the past, the CDC has recommended the administration of IG for departure within four weeks. However, a study in Kazahkstan found that the vaccine was effective post-exposure in preventing hepatitis A infection.2 The ACIP also updated recommendations for meningococcal vaccine, where minimum age is now lowered to 2 years of age. Adults may be immunized more than once with the vaccine, and the conjugate vaccine is preferred in individuals 55 years old and younger. In persons who had received the polysaccharide vaccine previously, revaccination is considered after 3-5 years.

Dr. Marano reported on the yellow fever vaccine-associated deaths in Peru (Ica), where four people have died recently following the vaccine. All were first-time recipients who received the vaccines during a yellow fever vaccination campaign, and one patient was reported to have lupus, although investigation is still being carried out at this time.

The CDC conducted an assessment of yellow fever vaccine prescribing practices in the United States, which surveyed pharmacies informally. There were 32 responses from 50 states: 25/32 responded that their state law did not permit dispensing/administering the vaccine, whereas 5/32 stated that they do so under the auspices of a licensed physician and stamp holder.

The new International Certificate of Vaccination or Prophylaxis (ICVP) took effect June 15, 2007. The old certificate is valid for 10 years. Travelers will need new certificates for vaccines administered after Dec. 15, 2007. The CDC had the new ICVP available December 1, 2007, at http://bookstore.gpo.gov.

Finally, Dr. Marano discussed the Beijing Olympics, which will take place Aug. 8-18, 2008, in seven cities. Paralympics will take place Sept. 6-17, 2008, in three cities. An estimated 1,200 athletes from the United States will travel to China for the events. The venues in eastern China are associated with possible concerns for Japanese encephalitis, a flavivirus. This is the leading cause of viral encephalitis in Asia, resulting in 50,000 cases per year. The Biken vaccine that has been used in the United States is no longer manufactured, and a new vaccine manufactured by Intercell is expected to be available in late 2008. This is a two-dose series. In view of the limited availability of JE vaccine and limited risk, the CDC does not anticipate recommending wide immunization of athletes or attendees to the Olympics. Clinicians should consider the anticipated exposure individually.

The Associate Editor thanks Drs. Paul Arguin and Nina Marano for their review and edits of this summary of their reports at the ASTMH meeting.

References:

  1. CDC. Update: prevention of hepatitis A after exposure to hepatitis A virus and in international travelers. Updated recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2007 56(41):1080-1084.
  2. Victor JC, et al. Hepatitis A vaccine versus immune globulin for postexposure prophylaxis. N Engl J Med 2007;357:1685-1694.