|
|
||||||||
| ABSTRACT |
|
|
|---|
| INTRODUCTION |
|
|
|---|
There is little published information regarding malaria risk among persons who live or work overseas.9 Malaria is a significant risk for military personnel deployed to Asia and Africa.1014 United States Peace Corps volunteers15 and persons that visit friends and relatives in malarious areas, especially in Africa, are at increased risk.16
The U.S. Department of State (DOS) Medical Program plays an important role in the prevention and treatment of illness among Foreign Service and other government personnel and their families stationed at overseas diplomatic posts. For patients with suspected or confirmed malaria, data forms are completed by DOS health care providers and sent to the Office of Medical Services of the DOS in Washington, DC. We evaluated these reports of malaria to describe the demographics of the affected population, determined the regions most affected by malaria infections, describe the frequency of Plasmodium species, identify the most common clinical complications associated with infection, assess prophylaxis usage by personnel with malaria, estimate the average annual incidence of malaria, and investigate malaria seasonality in Africa to better prevent this common and serious parasitic disease.
| METHODS |
|
|
|---|
Case report forms. A case report form (CRF) for malaria is requested for each case of suspected malaria under the care of the DOS medical program. The CRF contains demographic and laboratory data including the results of the malaria blood smear. Health care providers note clinical symptoms, presence of malaria-associated complications, reported use of chemoprophylaxis, and therapy prescribed.
The CRF, along with blood films, are forwarded to the Office of Medical Services in Washington, DC. The blood films are reviewed microscopically by a team of technologists experienced in malaria diagnosis as part of a laboratory quality improvement program.
To ensure patient confidentiality, a unique identifier was assigned to each patient. No personal identifiers were entered. Patient demographic characteristics and information on case reports were analyzed using Microsoft (Redmond, WA) Excel® and frequency tables were generated using SAS (Cary, NC) software applications.
Estimates of malaria incidence in African regions were calculated using number of new cases within each region17 divided by the number of persons assigned to posts during this period. For 19951999, the State Department Personnel and Staffing Division provided information on the authorized population at posts with health units for 1997. For 20002004, the total population at posts reported by health units for 2002 was used to estimate incidence. The latter included the number of adults and children. Because reporting from southern African posts is incomplete for 2002, the authorized number for 1999 is used.
Definition of terms. The following definitions were used in this report. Laboratory criteria for diagnosis was the demonstration of malaria parasites in blood smears determined to be P. falciparum, P. vivax, P. ovale, P. malariae, or Plasmodium species. A presumptive case is a person with symptoms compatible with malaria and treated without blood smear microscopic confirmation.
| RESULTS |
|
|
|---|
Among 684 cases with slide-demonstrated malaria parasites, the median age was 36 years (range = 9 months to 72 years). Most patients (64.8%) were 2049 years of age, 11.1% were 5059 years of age, and 2% were
60 years of age. Children less than five years of age comprised 4.1% and persons 519 years of age comprised 13.4%. For 4.5%, the age was not reported. There were 443 male (65%) and 235 female (34%) cases. For six cases, sex was not reported.
Patients with malaria worked for 11 different U.S. government agencies (Table 1
). The DOS, along with the U.S. Information Agency, which is now part of the DOS, accounted for 36.3% of cases. Personnel of the U.S. Agency for International Development (USAID) accounted for 30% of cases. Marine Security Guards make up the largest group of military personnel attached to posts and comprised at least 47 of 87 reports among Department of Defense personnel. U.S. Peace Corps staff and their eligible family members receive care from Department of State Health Units and Peace Corps volunteers generally receive care at Peace Corps Health Units.
|
|
|
Incidence of malaria.
The estimated incidence of malaria by regions of the world was highest in sub-Saharan Africa (Table 3
). The incidence in sub-Saharan Africa (Figure 2
) was more than 10 times higher than Asia, the area with the next highest rate. The number of cases and incidence during 20002004 was generally lower than 19951999. When we combined data from west, central and east Africa, the average incidence for 20002004 was higher in adults (average = 6.2/1,000/year) compared with 3.0/1,000/year for children less than 19 years of age.
|
|
|
Three deaths were reported (Table 4
). Two were more than 50 years of age (age was not reported for one). Only the Department of Defense employee was part of the DOS medical care system. Two patients reportedly had cerebral malaria. One was taking what is now considered inadequate prophylaxis, one took prophylaxis erratically, and one was not using chemoprophylaxis.
|
|
Comparison of results of microscopy and relationship to chemoprophylaxis.
Among 677 slides submitted to the Laboratory of the Office of Medical Services in Washington, DC over the 17 years, the Washington laboratory agreed with the local laboratory results for 552 (81.5%), including 486 positive and 66 negative. The Washington laboratory found parasites on 12 (1.8%) read as negative by the local laboratory. However, the major discrepancy was in slides read as positive for malaria parasites by local laboratories that could not be confirmed in Washington (n = 113). The Washington laboratory confirmed malaria parasites less frequently among those reportedly taking mefloquine (23 [51%] of 45 cases) compared with those taking chloroquine-based regimens (105 [87%] of 121 cases; P
0.001 by chi-square test).
| DISCUSSION |
|
|
|---|
Among 97 cases classified presumptively as malaria without slide-proven malaria, some were likely true cases and were therefore treated appropriately. However, an important alternative diagnosis may have been missed,18 patients may have been exposed unnecessarily to potentially toxic malaria treatment, and importantly, doubt about the effectiveness of chemoprophylaxis may have been introduced. Definitive diagnosis in resource-poor areas, continued quality improvement, and training of laboratory personnel are urgently needed.19,20
Although male adults were the group most affected by malaria, there were no available data on the distribution of sex, agency, or duration of exposure in the total post-population to make conclusions on infection and demographics. In west, central, and east Africa, the rate of malaria in children from 2000 through 2004 was less than half that of adults. One could theorize that workers who spend much time in the field such as USAID, Peace Corps staff, and agriculture-related Foreign Service personnel would be at greater risk, but data are lacking. Because most deaths from malaria in travelers occur in persons
50 years of age, increased education and prompt medical therapy for these persons may help reduce mortality caused by malaria.5,21
Plasmodium falciparum caused 83% of all cases of malaria reported in the present study. It is also responsible for the greatest number of reported infections worldwide, and causes the highest rate of complications and death.22 In contrast to our study, the proportion of cases of P. falciparum diagnosed and reported in the United States is lower, but has gradually increased from 30% at the beginning of the study period to 50% of the cases diagnosed in 2003 and 2004.5,23 Plasmodium vivax comprised 8.1% of cases in the present study, but 2224% of infections reported in the United States in 2003 and 2004. This may reflect the greater number of travelers from the United States to rural areas of Central and South America and the Indian sub-continent where P. vivax is more common. Among cases reported in the United States, P. malariae and P. ovale each make up approximately 3% of cases annually5 but were surprisingly uncommon among government personnel.
In the present study, 89.9% of cases were reportedly acquired in Africa. The proportion of cases acquired in Africa and diagnosed in the United States has increased from 37% in 1992 to 61% in 2004.5,23,24 In a recent study, Africa was the site of acquisition of malaria for 91.1% of European travelers.7 The proportion of patients with malaria was highest among those who had traveled to sub-Saharan Africa.18 Malaria rates in the present study and among Swedish travelers highlight the risk of malaria in Africa.25
Understanding the predominant species in various parts of the world is important in prescribing the most effective anti-malarial prophylaxis. For example, although atovaquone/proguanil is effective in preventing and treating P. falciparum infections, it appears to be less effective in preventing or treating P. vivax infections.26 Likewise, it is not effective in preventing hypnozoite-related relapses of P. vivax and P. ovale if used alone for treatment.27 One of our cases with P. vivax acquired in southeast Asia was treated with atovaquone/proguanil. Plasmodium vivax then relapsed some weeks later apparently from inadequate treatment for hypnozoites. Therefore, in areas with substantial P. vivax or P. ovale, primaquine, either as primary or terminal prophylaxis, might be a better choice, after testing for glucose-6-phosphate dehydrogenase.28,29
The number of patients with P. vivax who indicated they were not taking prophylaxis highlights two issues with P. vivax malaria. Cases with P. vivax and P. ovale malaria often occur weeks to months after leaving a malarious area.11,12,27 Second, and related, terminal prophylaxis or treatment with an 8-aminoquinoline such as primaquine is necessary to prevent late onset or relapses of these malarias.28
The study indicates that malaria cases peaked in the early 1990s among embassy personnel. Many of those cases occurred in Africa as chloroquine resistance developed across this continent.30,31 A study in Kampala, Uganda in 1992 in response to more cases among embassy personnel indicated one of the major problems was non-compliance with antimalarial medication.32 Furthermore, the study suggested chloroquine alone was no longer effective.32 The introduction of weekly mefloquine as the recommended prophylactic medication beginning in 199133 was temporally associated with a major decrease of cases across Africa in government personnel. The addition of atovaquone/proguanil in 200034 and primaquine in 200335 provide alternatives to mefloquine and doxycycline in these areas with chloroquine resistance.
Malaria risk in Africa changes seasonally. Although the months with greatest risk can often be predicted on the basis of increased temperature and rainfall, there is risk of malaria in every month in west, central, and east Africa. We speculate the reason for the high number of cases of malaria in January in west Africa may relate to prophylaxis irregularities during the end of year holidays, travel to rural areas, and increased outdoor activity in the dry season.
This study indicates the importance of preventing malaria to avoid complications and death. Cerebral malaria was reported in two of three of those cases with fatal outcomes. Prompt medical attention to those with fever and appropriate therapy are key to prevention of severe complications associated with malaria, especially for P. falciparum infections. Use of chemoprophylactic medication also reduces the risk of death.36 Additionally, our data confirm that persons more than 50 years of age may be at increased risk for complications including death.5,6
There are probably many reasons for the high numbers of cases of malaria in Foreign Service personnel. The increase in infected Anopheles mosquitoes and resistance to insecticides are probably the most important reasons for malaria risk, especially in Africa.37 The increase in resistance to chloroquine by P. falciparum and more recently by P. vivax in other areas is likely another.38 The underuse of personal anti-mosquito measures such as effective mosquito repellents, insecticide-impregnated bed nets, and protective clothing may be other contributing factors. Finally, the lack of proper and consistent use of chemoprophylactic measures is strongly suggested by this study.
In 2004, 75% of civilians with imported malaria in the United States had used an inappropriate or no chemoprophylactic regimen.5 Likewise, most Foreign Service persons with malaria were not taking regular chemoprophylaxis. Furthermore, in at least one instance, measurement of blood levels detected no mefloquine in someone who claimed regular use of the drug. Primary prevention (avoidance of Anopheles mosquito bites) and improved compliance to chemoprophylaxis are key.5,8,15,39 Effective, generally well-tolerated regimens of mefloquine, doxycycline, atovaquone/proguanil, and primaquine4042 have replaced ineffective30 and less safe prophylactic agents such as sulfadoxine/pyrimethamine42 and amodiaquine.43
Although trained health care workers completed case report forms, data on prophylaxis use were self-reported. In general, the use of self-reported data presents limitations for accuracy and validity. Few blood samples from malaria cases reporting use of mefloquine to detect blood drug and metabolite levels were available to confirm compliance and absorption. Study of P. falciparum isolates for drug sensitivity may be helpful.44 In addition, semi-quantitative information on patient use of personal protective measures (bed nets, insecticides, insect repellent, behavioral measures) as well as chemoprophylaxis may enable better detection of chemoprophylaxis failures and assist with compliance.
Another shortcoming is the lack of information gathered on vulnerable persons such as pregnant women and children. Because of concerns about the potential effects of chemoprophylaxis and the effects of malaria on pregnancy,45 additional information should be collected about chemoprophylaxis during pregnancy and pregnancy outcomes after malaria.46 Attention should also be given to the prevention of malaria in children of all ages through personal protective measures and an effective chemoprophylactic regimen.47,48
Another limitation is that only 89.5% of the 781 case reports reported to the Office of Medial Services were accompanied by blood smears. Some of these slides were of poor quality making confirmation difficult. A further study limitation is underreporting of cases and missing data on reports. We encourage reporting by giving feedback to providers and promoting the use of an updated form. Calculating incidence is complicated by the fact that the denominator of persons at risk for malaria at posts changes almost daily. The use of the actual number of persons at post as reported by health units monthly is probably a more accurate denominator than personnel authorization.
In conclusion, the study indicates those serving in sub-Saharan Africa are at the highest risk for malaria, especially P. falciparum. Many of the cases were taking what we now know was inadequate chemoprophylaxis because of parasite resistance. However, most persons who were infected with malaria did not take chemoprophylaxis, or took it irregularly. Recent drug development now provides four effective preventive drugs for those serving in Africa. Improved mosquito repellents and permethrin-treated bed nets and clothing are also now available. Continued training of laboratory personnel, ongoing laboratory quality improvement programs, field-adapted diagnostic technologies, and ongoing disease surveillance will improve the diagnosis of malaria. Proper and rapid diagnosis ensures all cases of malaria are promptly treated, cases of febrile illness that are not malaria are further investigated for preventable and treatable causes, and appropriate confidence is placed in properly used chemoprophylactic and personal protective regimens.
Received August 11, 2006. Accepted for publication October 2, 2006.
Acknowledgments: We thank Dr. Cedric Dumont (Director, Office of Medical Services, U.S. Department of State) for initiating the study, the medical technologists in Washington who reviewed the malaria slides, the technologists at overseas diplomatic posts who prepared and interpreted the malaria slides under field conditions, the medical providers who complete the case report forms and send the slides and reports for review, Dr. Robert Burney (Chief, Quality Improvement, U.S. Department of State) for support of monthly health unit reports from which the numbers of persons at post in 2002 are derived, the Department of Epidemiology and Biostatistics, The George Washington University (Washington, DC), Dr. Virginia Foster and Ann Goldman for their assistance.
Financial support: This study was supported by the United States Government. The American Society of Tropical Medicine and Hygiene (ASTMH) and the American Committee on Clinical Tropical Medicine and Travelers Health (ACCTMTH) assisted with publication expenses.
Disclaimer: The opinions expressed herein are those of the authors and are not to be construed as official nor necessarily represent the views or official policies of the Department of State or U.S. Government.
Disclosure: Martin Wolfe is a consultant for GlaxoSmithKline, the makers of atovaquone and proguanil (Malarone®). This statement is made in the interest of full disclosure and not because the author considers this to be a conflict of interest.
* Address correspondence to Joe P. Bryan, 1421 Mayflower Drive, McLean, VA 2210. E-mail: joe.p.bryan{at}earthlink.net ![]()
Authors addresses: Priya Joy Rathnam, U.S. Food and Drug Administration, Silver Spring, MD 20903. Joe P. Bryan, 1421 Mayflower Drive, McLean, VA 22101 Telephone: 703-356-8450, E-mail: joe.p.bryan{at}earthlink.net. Martin Wolfe, Travelers Medical Service, 2141 K Street, NW, Suite 408, Washington, DC 20037, Telephone: 202-466-8109.
| REFERENCES |
|
|
|---|
This article has been cited by other articles:
![]() |
C. K. Murray, R. A. Gasser Jr., A. J. Magill, and R. S. Miller Update on Rapid Diagnostic Testing for Malaria Clin. Microbiol. Rev., January 1, 2008; 21(1): 97 - 110. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |