Infectious Disease Challenges in Immigrants From Tropical Countries

DISCUSSION

Based on the history, clinical presentation, and laboratory data, the diagnoses of malaria and tuberculosis were considered. Because the peripheral smear revealed rare malarial parasite ring forms (trophozoites) and Schüffner's stippling, consistent with eitherP vivax or P ovale, the diagnosis of non-Plasmodium falciparum malaria was confirmed. Malaria is caused by 4 Plasmodium species: falciparum, vivax, ovale, and malariae. It can be contracted by the bite of the female Anopheles mosquito, by blood transfusion, or by organ transplant. An estimated 300 million to 500 million cases of malaria are diagnosed annually worldwide, leading to 1 million to 2 million deaths per year.^{1 ,2}According to the Centers for Disease Control and Prevention (CDC), the incidence of malaria in the United States in 1998 was 1381 cases.³ Nearly all reported cases involved travel outside the United States.

In addition to identification of the species, the peripheral blood smear will also reveal the parasite density (number of infected erythrocytes per 1000 erythrocytes). Higher parasite burdens are associated with poorer prognosis. Patients native to a region in which malaria is endemic have fewer complications attributable to partial immunity derived from repeated exposure to the organism. If a patient is infected with P falciparum, it is crucial to determine the geographic origin of the organism and the incidence of chloroquine resistance in the region. Chloroquine resistance in non-P falciparum species has also been noted.^{4 ,5} However, chloroquine remains the drug of choice unless there is no response or parasitemia continues.^{6 ,7}For current resistance patterns and treatment recommendations, the CDC should be contacted.

This patient presented with episodic fevers, chills, dark-colored urine, and anemia. In malaria, fevers are classically high, spiking, associated with sweating, and occur at regular intervals. A description of the fever pattern will often provide a clue to the particular malaria species. P ovale and P vivax present with a tertian fever that spikes regularly every 48 hours, whereas P malariae quartan fever cycles every 72 hours, and continuous fevers with intermittent irregular spikes are characteristic of P falciparum. Anemia is caused by the destruction of red blood cells when the schizonts are released. Hemoglobinuria may result in dark-colored urine. Splenic sequestration may result in thrombocytopenia.^{1 ,2}

Treatment should be initiated immediately after diagnosis by peripheral blood smear. Proper therapy is based on the Plasmodiumspecies, geographical origin of the parasite, parasite density, and the patient's clinical status.

The patient began a 3-day course of chloroquine, per the CDC. He had no adverse reactions to therapy. He then began a 14-day course of primaquine. However, before initiation of primaquine therapy, it is important to note that this patient's glucose-6-phosphate dehydrogenase was normal. If glucose-6-phosphate dehydrogenase activity had been low, primaquine could have induced a hemolytic anemia.^{1 ,2} After completion of therapy, no parasites were seen on peripheral blood smear.

Further history revealed the patient did receive bacille bilié de Calmette-Guérin as an infant; however, this should not produce such a strongly positive PPD. After receiving bacille bilié de Calmette-Guérin, patients will often develop reactivity <10 to 12 mm to PPD. This reactivity wanes in 3 to 5 years. The CDC and the American Thoracic Society recommend that any reactivity to PPD ≥10 mm be considered positive in foreign-born persons from Asia, Africa, or Latin America.⁹ Because of the patient's strongly reactive PPD and history suggesting exposure, the diagnosis of asymptomatic primary tuberculosis was made. The patient was started on isoniazid prophylaxis for 6 months.

An estimated one third of the world's population is infected with tuberculosis,¹⁰ which causes more deaths than any other infectious disease.¹¹ In today's mobile society, tuberculosis is just a plane flight away. The CDC reports that “the percentage of cases in foreign-born individuals increased from 27% of the national total in 1986 to 42% in 1998.”¹² This illustrates that the incidence of tuberculosis in the United States is disproportionately distributed among foreign-born persons.¹³ Tuberculosis is at least 10 times more prevalent in international children than in children born in the United State.¹⁴ One study found that of 83 pediatric refugees, 20% had reactive PPDs.¹⁵

This case illustrates the complexity of dealing with the international patient. Immigrants should be thoroughly screened on entering the United States. As demonstrated in this patient, these screening tests are not 100% sensitive and should not replace good clinical judgment. Studies have found that ∼50% of pediatric international adoptees have an undiagnosed medical condition on entering the United States.¹⁶ The problem of undiagnosed illness is even greater in the international refugee because of crowded conditions (ie, refugee camps), war, famine, and lack of a US sponsor. Often the international refugee will have sought care at other health care facilities, including emergency rooms and indigent care clinics, with little or no follow-up. This lack of continuity poses even greater concern for both the patient's well-being and general public health issues.

A review of the literature reveals the following recommendations concerning immigrant health screening^{14 ,16}:

1. Screening tests should be performed on the first visit because this may be the only patient contact.

2. A thorough history and physical examination should be performed, considering the diseases endemic to the patient's country of origin.

3. Infectious disease screening is necessary for HIV, hepatitis B, syphilis, stool for ova and parasites, and tuberculosis (PPD). Hepatitis B and HIV screening should be repeated in 6 months. Screening for hepatitis A is of little value because immunoglobulin G antibodies are almost ubiquitous.

4. All immigrants should have complete blood count with differential and a blood smear review.

5. Well-child issues including hearing, vision, weight, height, language, psychosocial, and immunization status should be addressed.

The CDC, its Morbidity Mortality Weekly Report, and its website (www.cdc.gov) are excellent resources for the generalist physician evaluating the health needs of our immigrants.