Emerging Vector-Borne Diseases
NOTE: On September 30, 2016 the Centers for Disease Control and Prevention (CDC) provided updated guidance on Zika virus for preconception planning in persons with potential exposure and prevention of transmission through sexual contact. The new interim guidance recommends that all men with possible exposure not only delay attempts for conception for at least 6 months beyond symptom onset, but also for 6 months beyond the last exposure if symptomatic.
This is an updated version of the article that appeared in print.
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Am Fam Physician. 2016 Oct 1;94(7):551-557.
Author disclosure: No relevant financial affiliations.
Several mosquito-borne viral infections have recently emerged in North America; West Nile virus is the most common in the United States. Although West Nile virus generally causes a self-limited, flulike febrile illness, a serious neuroinvasive form may occur. Dengue is the most common vector-borne viral disease worldwide, and it has been a significant public health threat in the United States since 2009. Known as breakbone fever for its severe myalgias and arthralgias, dengue may cause a hemorrhagic syndrome. Chikungunya also causes flulike febrile illness and disabling arthralgias. Although meningoencephalitis may occur with chikungunya, bleeding is uncommon. Symptoms of Zika virus infection are similar to those of dengue, but milder. Zika virus increases the risk of fetal brain abnormalities, including microcephaly, if a pregnant woman is infected. Zika virus is spread through Aedes albopictus mosquito bites, is transmitted sexually, and may rarely spread nonsexually from person to person. Diagnosis of these vector-borne infections is clinical and serologic, and treatment is supportive. Other, well-established vector-borne diseases are also important. Ehrlichiosis is a tick-borne bacterial disease that presents as a nonspecific syndrome of fever, headache, malaise, and myalgias. It is diagnosed via blood smear testing, with confirmatory serology. Ehrlichiosis is treated with doxycycline. Rickettsial infections are transmitted by fleas, mites, and ticks, and severity ranges from mild to life threatening. Rocky Mountain spotted fever, the most significant rickettsial infection, is primarily a clinical diagnosis that presents as fever, headache, myalgias, petechial rash, and tick exposure. Doxycycline is effective for rickettsial infections if administered promptly. Vector avoidance strategies are critical to the prevention of all of these infections.
Vector-borne diseases are infections that are primarily or exclusively transmitted through an invertebrate, generally insects.1 Some pathogens undergo an obligate stage of their life cycle inside the vector; others use the vector only for transport and inoculation. The most common vector-borne diseases are carried through mosquitoes and ticks. Vector-borne diseases account for 17% of all infections worldwide.1 The main impact of these diseases occurs abroad,1 but they are becoming more common in North America. Table 1 and Table 2 summarize common vector-borne diseases.
WHAT IS NEW ON THIS TOPIC: VECTOR-BORNE DISEASES
All pregnant women with a history of travel to a Zika virus outbreak area are advised to undergo viral testing and fetal ultrasonography.
Men with confirmed Zika virus infection should abstain from sexual intercourse or use condoms for six months after the onset of infection.
Men who have traveled to areas of Zika virus transmission but have no known infection should abstain from sexual intercourse or use condoms for at least six months after departure from the area. [Updated]
Rare nonsexual, person-to-person transmission of Zika virus has been reported.
SORT: KEY RECOMMENDATIONS FOR PRACTICE
|Clinical recommendation||Evidence rating||References||Comments|
Women who are pregnant or potentially pregnant should avoid travel to areas where Zika virus is spreading. If they choose to travel to these areas, mosquito avoidance measures should be taken.
Although malformation and microcephaly are associated with Zika virus infection, the risk of acquiring an infection when bitten by an infected mosquito and the risk of adverse fetal effects if infected are unknown.
Men with confirmed Zika virus infection should abstain from sexual intercourse or use condoms for six months after the onset of infection. Men who have traveled to areas of Zika virus transmission but have no known infection should abstain from sexual intercourse or use condoms for at least six months after departure from the area. [Updated]
Doxycycline is the drug of choice for rickettsial infections, even in children younger than eight years.
Benefit outweighs risk
Insect repellents with DEET 20% to 50% are effective for the prevention of many vector-borne diseases. Other agents such as picaridin, IR3535, and oil of lemon eucalyptus also appear to be effective.
Use in conjunction with physical barriers and other arthropod avoidance measures.
Insecticide-impregnated bed nets are effective for the prevention of mosquito-borne disease in endemic areas.
Significant benefit in decreasing incidence of malaria, a mosquito-borne infection
DEET = diethyltoluamide.
A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to http://www.aafp.org/afpsort.
SORT: KEY RECOMMENDATIONS FOR PRACTICE
|Clinical recommendation||Evidence rating||References||Comments|
Women who are pregnant or potentially pregnant should
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