Diseases Associated with Vectors Flashcards
African Tick Bite Fever
Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
Travelers to sub-Saharan Africa and the West Indies are at risk of infection. You may be at higher risk for African tick-bite fever if your travel plans include outdoor activities such as camping, hiking, and game hunting in wooded, brushy, or grassy areas. Ticks that are infected with tick-bite fever are usually most active from November through April.
Tick: R. africae - Sub-Saharan Africa, West Indies
prevention - Arthropod protection
Symptoms: African tick-bite fever should be suspected in a patient who presents with fever, headache, myalgia, and an eschar (tache noir) after recent travel to southern Africa. Diagnosis is usually based on clinical recognition and serology; the latter requires comparison of acute- to convalescent-phase serology, so is only helpful in retrospect. Etiologic agents can generally only be identified to the genus level by serologic testing. PCR and immunohistochemical analyses may also be helpful. Treatment of patients with possible rickettsioses should be started early and should not await confirmatory testing.
Treatment usually involves doxycycline. Chloramphenicol, azithromycin, fluoroquinolones, and rifampin may be alternatives, depending on the scenario. Expert advice should be sought if these alternative agents are being considered
Chikungunya
Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
CHIKV has been identified in many countries in Africa and Asia. Transmission has also been documented periodically in temperate areas, such as in Italy in 2007 and France in 2010. In late 2013, the first locally acquired cases of chikungunya were reported in the Americas on islands in the Caribbean. Most epidemics occur during the tropical rainy season and abate during the dry season. However, outbreaks in Africa have occurred after periods of drought, where open water containers served as vector-breeding sites. Risk of CHIKV infection exists throughout the day, as the primary vector, Ae. aegypti, aggressively bites during the daytime. Ae. aegypti mosquitoes bite indoors or outdoors near a dwelling. They typically breed in domestic containers that hold water, including buckets and flower pots.
Prevention No vaccine or preventive drug is available. The best way to prevent CHIKV infection is to avoid mosquito bites
Transmission CHIKV is transmitted via the bite of an infected mosquito of the Aedes spp., predominantly Aedes aegypti and Ae. albopictus. Nonhuman and human primates are likely the main reservoirs of the virus, and anthroponotic (human-to-vector-to-human) transmission occurs during outbreaks of the disease. Bloodborne transmission is possible; cases have been documented among laboratory personnel handling infected blood and a health care worker drawing blood from an infected patient. The risk of a person transmitting the virus to a biting mosquito or through blood is highest when the patient is viremic during the first 2–6 days of illness. Maternal-fetal transmission has been documented during pregnancy. The highest risk occurs when a woman is viremic at the time of delivery, with a vertical transmission rate of 49%. However, studies have not found CHIKV in breast milk.
Symptoms
approximately 3%–28% of people infected with CHIKV will remain asymptomatic. For people who develop symptomatic illness, the incubation period is typically 3–7 days (range, 2–12 days). Disease is most often characterized by sudden onset of high fever (temperature typically higher than 102°F [39°C]) and severe joint pain or stiffness. Other symptoms may include rash, headache, fatigue, nausea, vomiting, and myalgias. Fevers typically last from several days up to 1 week; the fever can be biphasic. Joint symptoms are severe and often debilitating. They are usually symmetric and occur most commonly in hands and feet, but they can affect more proximal joints. Rash usually occurs after onset of fever. It is typically maculopapular, involving the trunk and extremities, but can also include palms, soles, and face. Abnormal laboratory findings can include thrombocytopenia, lymphopenia, and elevated creatinine and liver function tests
Diagnosis
Preliminary diagnosis is based on the patient’s clinical features, places and dates of travel, and activities. Laboratory diagnosis is generally accomplished by testing serum to detect virus, viral nucleic acid, or virus-specific IgM and neutralizing antibodie Treatment
No specific antiviral treatment is available for chikungunya fever. Treatment is for symptoms and can include rest, fluids, and use of analgesics and antipyretics. Infected people should be protected from further mosquito exposure (staying indoors in areas with screens or under a mosquito net) during the first few days of the illness, so they do not contribute to the transmission cycle.
Dengue Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
Dengue is endemic throughout the tropics and subtropics and is a leading cause of febrile illness among travelers returning from the Caribbean, South America, and South and Southeast Asia. Although the geographic distribution of dengue is similar to that of malaria, dengue is more of a risk in urban and residential areas than is malaria
Prevention No vaccine is available, although several are in clinical trials; no chemoprophylaxis is available to prevent dengue. Travelers to dengue-endemic areas are at risk of getting dengue; risk increases with longer duration of travel and disease incidence in the travel destination (such as during dengue season and during epidemics). Travelers should be advised to avoid mosquito bites by taking the following preventive measures: Select accommodations with well-screened windows and doors or air conditioning when possible. Aedes mosquitoes typically live indoors and are often found in dark, cool places, such as in closets, under beds, behind curtains, and in bathrooms. Travelers should be advised to use insecticides to get rid of mosquitoes in these areas. Wear clothing that adequately covers the arms and legs, especially during the early morning and late afternoon, when risk of being bitten is the highest. Use insect repellent . For long-term travelers, empty and clean or cover any standing water that can be mosquito-breeding sites in the local residence (such as water storage tanks or flowerpot trays).
Transmission
Transmission occurs through the bite of an infected Aedes mosquito, primarily Aedes aegypti and Ae. albopictus. Humans are the main host and the primary source of virus for female mosquitoes, which become infective after an extrinsic incubation period of 8–12 days and can then transmit DENV for the rest of their approximately 1-month lifespan. Because of the approximately 7-day viremia in humans, bloodborne transmission is possible through exposure to infected blood, organs, or other tissues (such as bone marrow). In addition, perinatal DENV transmission occurs, and the highest risk appears to be among infants whose mothers are acutely ill around the time of delivery. It is not known if DENV is transmitted through breast milk.
Symptoms About 75% of all DENV infections are asymptomatic. Symptomatic infection (dengue) most commonly presents as a mild to moderate, nonspecific, acute, febrile illness. However, as many as 5% of all dengue patients develop severe, life-threatening disease. Early clinical findings are nonspecific but require a high index of suspicion, because recognizing early signs of shock and promptly initiating intensive supportive therapy can reduce risk of death among patients with severe dengue from 10% to <1%
Dengue begins abruptly after an incubation period of 4–7 days (range, 3–14 days), and the course follows 3 phases: febrile, critical, and convalescent. Fever typically lasts 2–7 days and can be biphasic. Other signs and symptoms may include severe headache; retroorbital pain; muscle, joint and bone pain; macular or maculopapular rash; and minor hemorrhagic manifestations, including petechiae, ecchymosis, purpura, epistaxis, bleeding gums, hematuria, or a positive tourniquet test result. Some patients have injected oropharynx and facial erythema in the first 24–48 hours after onset. Warning signs of progression to severe dengue occur in the late febrile phase around the time of defervescence and include persistent vomiting, severe abdominal pain, mucosal bleeding, difficulty breathing, signs of hypovolemic shock, and rapid decline in platelet count with an increase in hematocrit (hemoconcentration).
The critical phase of dengue begins at defervescence and typically lasts 24–48 hours. Most patients clinically improve during this phase, but those with substantial plasma leakage develop severe disease as a result of a marked increase in vascular permeability. Initially, physiologic compensatory mechanisms maintain adequate circulation, which narrows pulse pressure as diastolic blood pressure increases. Patients with severe plasma leakage have pleural effusions or ascites, hypoproteinemia, and hemoconcentration. Patients may appear to be well despite early signs of shock. However, once hypotension develops, systolic blood pressure rapidly declines, and irreversible shock and death may ensue despite resuscitation. Patients can also develop hemorrhagic manifestations, including hematemesis, bloody stool, melena, or menorrhagia, especially if they have prolonged shock. Dengue patients can have atypical manifestations, including hepatitis, myocarditis, pancreatitis, and encephalitis.
As the plasma leakage subsides, the patient enters the convalescent phase and begins to reabsorb extravasated intravenous fluids and pleural and abdominal effusions. As a patient’s well-being improves, hemodynamic status stabilizes (although he or she may manifest bradycardia), and diuresis ensues. The patient’s hematocrit stabilizes or may fall because of the dilutional effect of the reabsorbed fluid, and the white cell count usually starts to rise, followed by a slow recovery of platelet count. The convalescent-phase rash may desquamate and be pruritic.
Laboratory findings commonly include leucopenia, thrombocytopenia, hyponatremia, elevated aspartate aminotransferase and alanine aminotransferase, and a normal erythrocyte sedimentation rate.
Data are limited on health outcomes of dengue in pregnancy and effects of maternal DENV infection on the developing fetus. Perinatal DENV transmission can occur, and peripartum maternal infection may increase the likelihood of symptomatic disease in the newborn. Of the 34 perinatal transmission cases described in the literature, all developed thrombocytopenia and all but 1 had fever in the first 2 weeks after birth. Nearly 40% had a hemorrhagic manifestation, and one-fourth had hypotension. Transplacental transfer of maternal IgG anti-DENV (from a previous maternal infection) may increase risk for severe dengue among infants infected at 6–12 months of age.
Treatment
No specific antiviral agents exist for dengue. Patients should be advised to stay well hydrated and to avoid aspirin (acetylsalicylic acid), aspirin-containing drugs, and other nonsteroidal anti-inflammatory drugs (such as ibuprofen) because of their anticoagulant properties. Fever should be controlled with acetaminophen and tepid sponge baths. Febrile patients should avoid mosquito bites to reduce risk of further transmission. For those who develop severe dengue, close observation and frequent monitoring in an intensive care unit setting may be required. Prophylactic platelet transfusions in dengue patients are not beneficial and may contribute to fluid overload.
Japanese Encephalitis Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
JE virus is the most common vaccine-preventable cause of encephalitis in Asia, occurring throughout most of Asia and parts of the western Pacific Transmission principally occurs in rural agricultural areas, often associated with rice cultivation and flood irrigation. In some areas of Asia, these ecologic conditions may occur near, or occasionally within, urban centers. In temperate areas of Asia, transmission is seasonal, and human disease usually peaks in summer and fall. In the subtropics and tropics, seasonal transmission varies with monsoon rains and irrigation practices and may be prolonged or even occur year-round. In endemic countries, where adults have acquired immunity through natural infection, JE is primarily a disease of children. However, travel-associated JE can occur among people of any age. For most travelers to Asia, the risk for JE is extremely low but varies based on destination, duration, season, and activities.
Prevention
Athropod protection Vaccine One JE vaccine is licensed and available in the United States—an inactivated Vero cell culture–derived vaccine, Ixiaro . Ixiaro, manufactured by Intercell and distributed by Novartis Vaccines, was approved in March 2009 for use in people aged ≥17 years and in May 2013 for use in children aged 2 months through 16 years. Other inactivated and live attenuated JE vaccines are manufactured and used in other countries but are not licensed for use in the United States. Indications for Use of JE Vaccine for Travelers When making recommendations regarding the use of JE vaccine for travelers, clinicians must weigh the overall low risk of travel-associated JE, the high rate of death and disability when JE occurs, the low probability of serious adverse events after immunization, and the cost of the vaccine. Evaluation of a traveler’s risk should take into account the planned itinerary, including travel location, duration, activities, and seasonal patterns of disease in the areas to be visited . The data in the table should be interpreted cautiously, because JE virus transmission activity varies within countries and from year to year. The Advisory Committee on Immunization Practices recommends JE vaccine for travelers who plan to spend ≥1 month in endemic areas during the JE virus transmission season. This includes long-term travelers, recurrent travelers, or expatriates who will be based in urban areas but are likely to visit endemic rural or agricultural areas during a high-risk period of JE virus transmission. Vaccine should also be considered for the following:
- Short-term (<1 month) travelers to endemic areas during the JE virus transmission season, if they plan to travel outside an urban area and their activities will increase the risk of JE virus exposure. Examples of higher-risk activities or itineraries include 1) spending substantial time outdoors in rural or agricultural areas, especially during the evening or night; 2) participating in extensive outdoor activities (such as camping, hiking, trekking, biking, fishing, hunting, or farming); and 3) staying in accommodations without air conditioning, screens, or bed nets.
- Travelers to an area with an ongoing JE outbreak.
- Travelers to endemic areas who are uncertain of specific destinations, activities, or duration of travel
JE vaccine is not recommended for short-term travelers whose visits will be restricted to urban areas or times outside a well-defined JE virus transmission season.
Transmission:
JE virus is transmitted to humans through the bite of an infected mosquito, primarily Culex species. The virus is maintained in an enzootic cycle between mosquitoes and amplifying vertebrate hosts, primarily pigs and wading birds. Humans are incidental or dead-end hosts, because they usually do not develop a level or duration of viremia sufficient to infect mosquitoes.
Symptoms:
Most human infections with JE virus are asymptomatic; <1% of people infected with JE virus develop clinical disease. Acute encephalitis is the most commonly recognized clinical manifestation of JE virus infection. Milder forms of disease, such as aseptic meningitis or undifferentiated febrile illness, can also occur. The incubation period is 5–15 days. Illness usually begins with sudden onset of fever, headache, and vomiting. Mental status changes, focal neurologic deficits, generalized weakness, and movement disorders may develop over the next few days.
- The classical description of JE includes a parkinsonian syndrome with masklike facies, tremor, cogwheel rigidity, and choreoathetoid movements.
- Acute flaccid paralysis, with clinical and pathological features similar to those of poliomyelitis, has also been associated with JE virus infection.
- Seizures are common, especially among children.
- Common clinical laboratory findings include moderate leukocytosis, mild anemia, and hyponatremia. Cerebrospinal fluid (CSF) typically has a mild to moderate pleocytosis with a lymphocytic predominance, slightly elevated protein, and normal ratio of CSF to plasma glucose.
The case-fatality ratio is approximately 20%–30%. Among survivors, 30%–50% have serious neurologic, cognitive, or psychiatric sequelae.
Treatment:
There is no specific antiviral treatment for JE; therapy consists of supportive care and management of complications.
Tick Borne Encephalitis Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
TBE is endemic in focal areas of Europe and Asia (from eastern France to northern Japan and from northern Russia to Albania) Russia has the largest number of reported TBE cases, and western Siberia has the highest incidence of TBE in the world. Other European countries with known endemic areas include Austria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Lithuania, Norway, Poland, Romania, Slovakia, Slovenia, Sweden, and Switzerland. Asian countries with reported TBE cases or virus activity include China, Japan, Kazakhstan, Kyrgyzstan, Mongolia, and South Korea. Most cases occur from April through November, with peaks in early and late summer when ticks are active. The incidence and severity of disease are highest in people aged ≥50 years.
Most cases occur from April through November, with peaks in early and late summer when ticks are active. The incidence and severity of disease are highest in people aged ≥50 years. Most cases occur in areas <2,500 ft (750 m). In the last 30 years, the geographic range of TBEV appears to have expanded to new areas, and the virus has been found at altitudes up to and above 5,000 ft (1,500 m). These trends are likely due to a complex combination of changes in diagnosis and surveillance, human activities and socioeconomic factors, and ecology and climate.
The overall risk of acquiring TBE for an unvaccinated visitor to a highly endemic area during the TBEV transmission season has been estimated at 1 case per 10,000 person-months of exposure. Most TBEV infections result from tick bites acquired in forested areas through activities such as camping; hiking; fishing; bicycling; collecting mushrooms, berries, or flowers; and outdoor occupations such as forestry or military training. The risk is negligible for people who remain in urban or unforested areas and who do not consume unpasteurized dairy products.
Vector tick population density and infection rates in TBEV-endemic foci are highly variable. For example, TBEV infection rates in I. ricinus in central Europe vary from <0.1% to approximately 5%, depending on geographic location and time of year, while rates of up to 40% have been reported in I. persulcatus in Siberia. The number of TBE cases reported from a country depends on the ecology and geographic distribution of TBEV, the intensity of diagnosis and surveillance, and the vaccine coverage in the population. Therefore, the number of human TBE cases reported from an area may not be a reliable predictor of a traveler’s risk for infection.
Prevention:
Travelers should avoid consuming unpasteurized dairy products and use all measures to avoid tick bites
Vaccine
Transmission:
TBEV is transmitted to humans through the bite of an infected tick of the Ixodes species, primarily I. ricinus (European subtype) or I. persulcatus (Siberian and Far Eastern subtypes). The virus is maintained in discrete areas of deciduous forests. Ticks act as both vector and virus reservoir, and small rodents are the primary amplifying host. Tickborne encephalitis (TBE) can also be acquired by ingesting unpasteurized dairy products (such as milk and cheese) from infected goats, sheep, or cows. TBEV transmission has infrequently been reported through laboratory exposure and slaughtering viremic animals. Direct person-to-person spread of TBEV occurs only rarely, through blood transfusion or breastfeeding.
Symptoms:
Approximately two-thirds of infections are asymptomatic. The median incubation period for TBE is 8 days (range, 4–28 days). The incubation period for milkborne exposure is usually shorter (3–4 days). Acute neuroinvasive disease is the most commonly recognized clinical manifestation of TBEV infection. However, TBE disease often presents with milder forms of the disease or a biphasic course:
- First phase: nonspecific febrile illness with headache, myalgia, and fatigue. Usually lasts for several days and may be followed by an afebrile and relatively asymptomatic period. Up to two-thirds of patients may recover without any further illness.
- Second phase: central nervous system involvement resulting in aseptic meningitis, encephalitis, or myelitis. Findings include meningeal signs, altered mental status, cognitive dysfunction, ataxia, tremors, cranial nerve palsies, and limb paresis.
Disease severity increases with age. Clinical course and long-term outcome also vary by TBEV subtype:
- The European subtype is associated with milder disease, a case-fatality ratio of <2%, and neurologic sequelae in up to 30% of patients.
- The Far Eastern subtype is often associated with a more severe disease course, including a case-fatality ratio of 20%–40% and higher rates of severe neurologic sequelae.
- The Siberian subtype is more frequently associated with chronic or progressive disease and has a case-fatality ratio of 2%–3%.
TBE should be suspected in travelers who develop a nonspecific febrile illness that progresses to neuroinvasive disease within 4 weeks of arriving from an endemic area. A history of tick bite may be a clue to this diagnosis; however, approximately 30% of TBE patients do not recall a tick bite.
Treatment
There is no specific antiviral treatment for TBE; therapy consists of supportive care and management of complications.
Filariasis Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
Found in sub-Saharan Africa, Egypt, southern Asia, the western Pacific Islands, the northeastern coast of Brazil, Guyana, Haiti, and the Dominican Republic. Travelers are at low risk. Nematode infection
Prevention: Mosquito precautions
Transmission
Through the bite of infected Aedes, Culex, Anopheles, and Mansonia mosquitoes.
Symptoms: Most infections are asymptomatic, but lymphatic dysfunction may lead to lymphedema of the leg, scrotum, penis, arm, or breast years after infection. Acute episodes are associated with painful swelling of an affected limb, fever, or chills due to bacterial superinfection. Tropical pulmonary eosinophilia is a potentially serious progressive lung disease that presents with nocturnal cough, wheezing, and fever, resulting from immune hyperresponsiveness to microfilariae in the pulmonary capillaries
Treatment
The drug of choice, diethylcarbamazine, can be obtained from CDC under an investigational new drug protocol (404-718-4745; parasites@cdc.gov). Patients with lymphedema and hydrocele can benefit from lymphedema management and, in the case of hydrocele, surgical repair.
Loa Loa Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
The parasite is passed from deerflies to humans in certain rain forests of West and Central Africa. The deerflies usually bite during the day and are more common during the rainy season. They are attracted by the movement of people and by smoke from wood fires. Rubber plantations may be an area where many deerflies are found. Your health care provider can help you determine if you are going to or have been to an area where loiasis is found.
Prevention: Avoid insect bites by wearing long pants and long-sleeved shirts and avoid the smoke of wood fires to reduce your risk of infection. If you are going to stay in an area affected by Loa loa in West and Central Africa for a long period of time, you can reduce your risk of getting loiasis by taking DEC weekly. You should consult a tropical medicine expert to determine whether using DEC to prevent loiasis is right for you. It can take time to get DEC, so do not wait until the last minute.
Transmission
You get infected by being bitten by an infected deerfly of the genus Chrysops. Deerflies become infected when they eat blood from an infected person. Travelers are more likely to become infected if they are in areas where they are bitten by deerflies for many months, though occasionally they get infected even if they are in the area for less than 30 days
Symptoms
Many people do not develop any symptoms, and symptoms usually do not show up for many months after infection. If you have loiasis, you may have itchy, non-painful swellings of the body that come and go. The swellings can show up anywhere though they are more common near joints. You may develop an eye worm that crawls across the surface of your eye. Sometimes you may see a worm that crawls under your skin. Less common symptoms include itching all over your body, muscle pain, joint pain, and fatigue. Blood tests may show high counts of eosinophils, which are a type of blood cell that can be associated with parasitic infections.
Treatment
Sometimes treatment of loiasis can be dangerous, so your health care provider may want to talk to an expert in tropical medicine before giving you any medication to treat loiasis. If you have an eye worm, the worm can be surgically removed to provide immediate relief while your health care provider determines if it is safe to treat you with medication to kill the parasite. Removing the worm from your eye does not cure the infection, as the parasite is often found in other parts of your body. A medication called diethylcarbamazine, or DEC, can be used to kill the parasites in your body. Because there is a small risk of serious side effects related to killing the parasites, your health care provider will do tests to be sure that it is safe to treat you. Sometimes people need special treatments before it is safe to give medication and sometimes treatment with medications is not recommended.
Onchocerciasis Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
Endemic in central Africa. Small endemic foci are also present in the Arabian Peninsula (Yemen) and in the Americas (Brazil, Colombia, Ecuador, Guatemala, southern Mexico, and Venezuela). Most infections, outside those in endemic populations, occur in expatriate groups, such as missionaries, field scientists, and Peace Corps volunteers.
Prevention
Avoid blackfly habitats (free-flowing rivers and streams) and use protection measures against biting insects
Transmission Through female blackflies (genus Simulium), which typically bite during the day and near rapidly flowing rivers and streams.
Symptoms
Highly pruritic, papular dermatitis; subcutaneous nodules; lymphadenitis; and ocular lesions, which can progress to visual loss and blindness. Symptomsin travelers are primarily dermatologic and may occur months to years after departure from endemic areas.
Treatment:
Ivermectin is the drug of choice. Repeated annual or semiannual doses may be required, as the drug kills the microfilariae but not the adult worms. Some experts recommend treating patients with 1 dose of ivermectin followed by 6 weeks of doxycycline. Diethylcarbamazine is contraindicated in onchocerciasis, because it has been associated with severe and fatal post-treatment reactions. An expert in tropical medicine should be consulted to help manage these patients
Hemorrhagic Fevers
Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
The viruses that cause VHFs are distributed over much of the globe. Each virus is associated with ≥1 nonhuman host or vector species, restricting the virus and the initial contamination to the areas inhabited by these species. The diseases caused by these viruses are seen in people living in or having visited these areas. Humans are incidental hosts for these enzootic diseases; however, person-to-person transmission of some viruses can result in large human outbreaks
Ebola and Marburg: Filoviral Diseases Ebola and Marburg viruses cause hemorrhagic fever in humans and nonhuman primates. Five species of Ebola virus have been identified: Côte d’Ivoire, Sudan, Zaire, Bundibugyo, and Reston. Countries with confirmed human cases of Ebola hemorrhagic fever include Republic of the Congo, Côte d’Ivoire, Democratic Republic of the Congo, Gabon, Sudan, and Uganda. Ebola-Reston virus is believed to be endemic in the Philippines and potentially in neighboring countries but has not been shown to cause human disease. Countries with confirmed human cases of Marburg hemorrhagic fever include Angola, Democratic Republic of the Congo, Kenya, Uganda, and possibly Zimbabwe. Growing evidence indicates that fruit bats are the natural reservoir for filoviruses. Outbreaks occur when a person becomes infected after exposure to the reservoir species or a secondarily infected nonhuman primate and then transmits the virus to other people in the community. Four cases of Marburg hemorrhagic fever have occurred in travelers visiting caves harboring bats, including Kitum cave in Kenya and a python cave in Maramagambo Forest, Uganda. Miners have also acquired Marburg infection from working in underground mines harboring bats in the Democratic Republic of the Congo and Uganda.
Lassa Fever and Other Arenaviral Diseases Arenaviruses are transmitted from rodents to humans, except Tacaribe virus, which was found in bats. Most infections are mild, but some result in hemorrhagic fever with high death rates. Old World (Eastern Hemisphere) and New World (Western Hemisphere) viruses cause the following diseases:
- Old World viruses: Lassa virus (Lassa fever) lymphocytic choriomeningitis virus (meningitis, encephalitis, and congenital fetal infection in normal hosts, hemorrhagic fever in organ transplant recipients). Lassa fever occurs in rural West Africa, with hyperendemic areas in Guinea, Liberia, Nigeria, and Sierra Leone. Lujo virus has been recently described in Zambia and the Republic of South Africa during a health care–associated outbreak.
- New World viruses: Junin (Argentine hemorrhagic fever), Machupo (Bolivian hemorrhagic fever), Guanarito (Venezuelan hemorrhagic fever), Sabia (Brazilian hemorrhagic fever), and the recently discovered Chapare virus (a single case in Bolivia). Reservoir host species are Old World rats and mice (family Muridae, subfamily Murinae) and New World rats and mice (family Muridae, subfamily Sigmodontinae). These rodent types are found worldwide, including Europe, Asia, Africa, and the Americas. Virus is transmitted through inhalation of aerosols from rodent urine, ingestion of rodent-contaminated food, or direct contact of broken skin or mucosa with rodent excreta. Risk of Lassa virus infection is associated with peridomestic rodent exposure. Inappropriate food storage increases the risk for exposure. Health care–associated transmission of Lassa, Lujo, and Machupo viruses has occurred through droplet and contact. One anecdotal report of possible airborne transmission exists. Several cases of Lassa fever have been confirmed in international travelers staying in traditional dwellings in the countryside.
Rift Valley Fever and Other Bunyaviral Diseases
RVF causes fever, hemorrhage, encephalitis, and retinitis in humans, but primarily affects livestock. RVF is endemic to sub-Saharan Africa. Sporadic outbreaks have occurred in humans in Egypt, Madagascar, and Mauritania. Large epidemics occurred in Kenya, Somalia, and Tanzania in 1997–1998 and 2006–2007; Saudi Arabia and Yemen in 2000; Madagascar in 2008; and South Africa, Botswana, Namibia, and Mauritania in 2010. RVF virus is transmitted by mosquito, percutaneous inoculation, and slaughter or consumption of infected animals. CCHF is endemic where ticks of the genus Hyalomma are found in Africa and Eurasia, including South Africa, the Balkans, the Middle East, Russia, and western China, and is highly endemic in Afghanistan, Iran, Pakistan, and Turkey. CCHF virus is transmitted to humans by infected ticks or direct handling and preparation of fresh carcasses of infected animals, usually domestic livestock. Health care–associated transmission often occurs. Hantaviruses cause hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). The viruses that cause HPS are present in the New World; those that cause HFRS occur worldwide. The viruses that cause both HPS and HFRS are transmitted to humans through contact with urine, feces, or saliva of infected rodents. Travelers staying in rodent-infested dwellings are at risk for HPS and HFRS. Human-to-human transmission has been reported only with Andes virus in Chile and Argentina.
Prevention:
The risk of acquiring VHF is low for international travelers. Travelers at increased risk for exposure include those engaging in animal research, health care workers, and others providing care for patients in the community, particularly where outbreaks of VHF are occurring. Prevention should focus on avoiding contact with host or vector species in endemic countries. Travelers should not visit locations where an outbreak is occurring, avoid contact with rodents and bats, and avoid livestock in RVF- and CCHF-endemic areas. To prevent vectorborne disease, travelers should use insecticide-treated bed nets and wear insect repellent. Standard precautions and contact and droplet precautions for suspected VHF case-patients are recommended to avoid transmission. Direct contact should be avoided with corpses of patients suspected of having died of Ebola, Marburg, or Old World arenavirus infection. Contact with or consumption of primates, bats, and other bushmeat should be avoided. Bat-inhabited caves or mines should be avoided. Investigational vaccines exist for Argentine hemorrhagic fever and RVF; however, neither is approved by FDA nor are they commonly available in the United States.
Transmission: Some VHFs are spread person to person through direct contact with symptomatic patients, body fluids, or cadavers or through inadequate infection control in a hospital setting (filoviruses, arenaviruses, CCHF virus). Zoonotic spread may occur from contact with the following: Livestock via slaughter or consumption of raw meat from infected animals and, potentially, unpasteurized milk (CCHF, RVF, Alkhurma viruses) Bushmeat, likely via slaughter or consumption of infected animals (Ebola, Marburg viruses) Rodents via inhalation of or contact with materials contaminated with rodent excreta (arenaviruses, hantaviruses) Other reservoir species, such as bats (Ebola, Marburg viruses) Vectorborne transmission also occurs via mosquito (RVF virus) or tick (CCHF, Omsk, Kyasanur Forest disease, Alkhurma viruses) bites or by crushing infected ticks.
Symptoms:
Signs and symptoms vary by disease, but in general, patients with VHF present with abrupt onset of fever, myalgias, and prostration, followed in severe forms by coagulopathy with a petechial rash or ecchymoses and sometimes overt bleeding. Vascular endothelial damage leads to shock and pulmonary edema; liver injury is common. Signs seen with specific viruses include renal failure (HFRS); ecchymoses and bruises (CCHF); hearing loss, anasarca and shock in newborns (Lassa fever); and spontaneous abortion and birth defects (Lassa and lymphocytic choriomeningitis viruses). Because the incubation period may be as long as 21 days, patients may not develop illness until returning from travel; therefore, a thorough travel and exposure history is critical.
Treatment: Ribavirin is effective for treating Lassa fever and other Old World arenaviruses, New World arenaviruses, and potentially CCHF, but it is not approved by the Food and Drug Administration (FDA) for these indications
Leishmaniasis - cutaneous Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
In the Old World (Eastern Hemisphere), CL is found in parts of the Middle East, Asia (particularly southwest and central Asia), Africa (particularly the tropical region and North Africa), and southern Europe. In the New World (Western Hemisphere), CL is found in parts of Mexico, Central America, and South America. Occasional cases have been reported in Texas and Oklahoma. CL is not found in Chile, Uruguay, or Canada. Overall, CL is found in focal areas of >90 countries. Most (up to 90%) of the world’s cases of CL occur in only a few of those countries: Afghanistan, Algeria, Iran, Iraq, Saudi Arabia, and Syria in the Old World; and Bolivia, Brazil, Colombia, Nicaragua, and Peru in the New World
Prevention: No vaccines or drugs to prevent infection are available.
Preventive measures are aimed at reducing contact with sand flies by using personal protective measures. Travelers should be advised to: Avoid outdoor activities, especially from dusk to dawn, when sand flies generally are the most active. Wear protective clothing and apply insect repellent to exposed skin and under the edges of clothing, such as sleeves and pant legs, according to the manufacturer’s instructions. Sleep in air-conditioned or well-screened areas. Spraying the quarters with insecticide might provide some protection. Fans or ventilators might inhibit the movement of sand flies, which are weak fliers. Sand flies are so small (approximately 2–3 mm, less than one-eighth of an inch) that they can pass through the holes in ordinary bed nets. Although closely woven nets are available, they may be uncomfortable in hot climates. The effectiveness of bed nets can be enhanced by treatment with a pyrethroid-containing insecticide. The same treatment can be applied to window screens, curtains, bed sheets, and clothing. The risk is highest from dusk to dawn because sand flies typically feed (bite) at night and during twilight hours. Although sand flies are less active during the hottest time of the day, they may bite if they are disturbed (for example, if hikers brush against tree trunks or other sites where sand flies are resting). Vector activity can easily be overlooked: sand flies do not make noise, they are small (approximately one-third the size of mosquitoes), and their bites might not be noticed. Examples of types of travelers who might have an increased risk for CL include ecotourists, adventure travelers, bird watchers, Peace Corps volunteers, missionaries, military personnel, construction workers, and people who do research outdoors at night or twilight. However, even short-term travelers in endemic areas have developed CL.
Transmission:
CL is transmitted through the bite of an infected female phlebotomine sand fly. CL also can occur after accidental occupational (laboratory) exposures to Leishmania parasites.
Symptoms:
CL is characterized by skin lesions (open or closed sores), which typically develop within several weeks or months after exposure. In some people, the sores first appear months or years later, in the context of trauma (such as skin wounds or surgery). The sores can change in size and appearance over time. They typically progress from small papules to nodular plaques, and eventually lead to open sores with a raised border and central crater (ulcer), which can be covered with scales or crust. The lesions usually are painless but can be painful, particularly if open sores become infected with bacteria. Satellite lesions, regional lymphadenopathy (swollen glands), and nodular lymphangitis can be noted. The sores usually heal eventually, even without treatment. However, they can last for months or years and typically result in scarring. A potential concern applies to some of the Leishmania species in South and Central America: some parasites can spread from the skin to the mucosal surfaces of the nose or mouth and cause sores there. This form of leishmaniasis, mucosal leishmaniasis (ML), might not be noticed until years after the original skin sores appear to have healed. Although ML is uncommon, it has occurred in travelers and expatriates whose cases of CL were not treated or were inadequately treated. The initial clinical manifestations typically involve the nose (chronic stuffiness, bleeding, and inflamed mucosa or sores) and less often the mouth; in advanced cases, ulcerative destruction of the nose, mouth, and pharynx can be noted (such as perforation of the nasal septum).
Treatment: Decisions about whether and how to treat CL should be individualized. All cases of ML should be treated; there are several therapeutic options.
Leishmaniasis - Visceral Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
VL is usually more common in rural than urban areas, but it is found in some periurban areas (such as in northeastern Brazil). In the Old World (Eastern Hemisphere), VL is found in parts of Asia (particularly the Indian subcontinent and southwest and central Asia), the Middle East, Africa (particularly East Africa), and southern Europe. In the New World (Western Hemisphere), most cases occur in Brazil; some cases occur in scattered foci elsewhere in Latin America. Overall, VL is found in focal areas of >60 countries. Most (>90%) of the world’s cases of VL occur in the Indian subcontinent (India, Bangladesh, and Nepal), East Africa (Sudan, South Sudan, and Ethiopia), and Brazil; none of the affected areas in these 7 countries are common tourist destinations
Prevention: No vaccines or drugs to prevent infection are available. Preventive measures are aimed at reducing contact with sand flies Transmission VL is predominantly transmitted through the bite of an infected female phlebotomine sand fly, although congenital and parenteral transmission (through blood transfusions and needle sharing) have been reported.
Symptoms: Among symptomatic people, the incubation period typically ranges from weeks to months. The onset of illness can be abrupt or gradual. Stereotypical manifestations of VL include fever, weight loss, hepatosplenomegaly (especially splenomegaly), and pancytopenia (anemia, leukopenia, and thrombocytopenia). If untreated, severe (advanced) cases of VL typically are fatal. Latent infection can become clinically manifest years to decades after exposure in people who become immunocompromised for other medical reasons.
Treatment
Infected travelers should be advised to consult an infectious disease or tropical medicine specialist. Therapy for VL should be individualized with expert consultation.
Lyme Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
In Europe, endemic from southern Scandinavia into the northern Mediterranean countries of Italy, Spain, and Greece. Incidence is highest in central and Eastern European countries. In North America, highly endemic areas are the northeastern and north-central United States. Transmission has not been documented in the tropics. Lyme disease is rarely reported in returning travelers.
Prevention:
Avoid tick habitats, use insect repellent on exposed skin and clothing, and carefully check every day for attached ticks. Minimize areas of exposed skin by wearing long-sleeved shirts, long pants, and closed shoes; tucking shirts in and tucking pants into socks may also reduce risk
Transmission
Through the bite of Ixodes ticks; infected people are often unaware that they have been bitten.
Symptoms
Incubation period is typically 3–30 days. Approximately 80% of people infected with B. burgdorferi develop a characteristic rash, erythema migrans (EM), within 30 days of exposure. EM is a red, expanding rash, with or without central clearing, that is often accompanied by symptoms of fatigue, fever, headache, mild stiff neck, arthralgia, or myalgia. Within days or weeks, infection can spread to other parts of the body, causing more serious neurologic conditions (meningitis, radiculopathy, and facial palsy) or cardiac abnormalities (myocarditis with atrioventricular heart block). Untreated, infection can progress over a period of months to cause monoarticular or oligoarticular arthritis, peripheral neuropathy, or encephalopathy. These long-term sequelae can be typically observed over a number of months, ranging from 1 week to a few years.
Treatment
Most patients can be treated with either oral doxycycline or intravenous ceftriaxone.
Anaplasma Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
Human Anaplasma infections are most commonly reported in the United States but can occur more rarely in Europe and Asia. The agent occurs worldwide, corresponding with the ranges of I. persulcatus group ticks. Although nonpathogenic genetic variants are common worldwide in many vertebrate hosts, human pathogenic types are present in rodent and small-mammal reservoirs in North America and in deer (roe and red) and wild boar in Europe.
Prevention
No vaccine is available for preventing rickettsial infections. Antibiotics are not recommended for prophylaxis of rickettsial diseases. Travelers should be instructed to minimize exposure to infectious arthropods (including lice, fleas, ticks, mites) and animal reservoirs, particularly dogs and cats, when traveling in endemic areas. The proper use of insect or tick repellents or insecticides and acaricides, self-examination after visits to vector-infested areas, and wearing protective clothing are ways to reduce risk. These precautions are especially important for people with underlying conditions that may compromise their immune systems, as these people may be more susceptible to severe disease.
Transmission
Most rickettsial pathogens are transmitted by ectoparasites such as fleas, lice, mites, and ticks during feeding or by scratching crushed arthropods or infectious feces into the skin. Inhaling dust or inoculating conjunctiva with infectious material may also cause infection. Tick - Small mammals, rodents, and deer - Primarily United States, worldwide
Symptoms
Rickettsioses are difficult to specifically diagnose, even by physicians experienced with these diseases. Clinical presentations vary with the causative agent and patient; however, common symptoms that typically develop within 1–2 weeks of infection include fever, headache, malaise, and sometimes nausea and vomiting. Most symptoms associated with acute rickettsial infections are nonspecific. Many rickettsioses are accompanied by a maculopapular, vesicular, or petechial rash or an eschar at the site of the tick bite. Ehrlichiosis and anaplasmosis should be suspected in febrile patients with leukopenia and transaminitis with an exposure history. Most symptomatic rickettsial diseases cause moderate illness, but epidemic typhus and Rocky Mountain spotted fever can be severe and may be fatal in 20%–60% of untreated cases.
Treatment
Treatment of patients with possible rickettsioses should be started early and should not await confirmatory testing. Treatment usually involves doxycycline. Chloramphenicol, azithromycin, fluoroquinolones, and rifampin may be alternatives, depending on the scenario. Expert advice should be sought if these alternative agents are being considered.
Babesia Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
Most cases occur in the Northeast and upper Midwest, particularly in parts of New England, New York state, New Jersey, Wisconsin, and Minnesota. In the Northeast, babesiosis occurs in both inland and coastal areas, including off-shore islands, such as Nantucket and Martha’s Vineyard (Massachusetts); Block Island (Rhode Island); and Shelter Island, Fire Island, and eastern Long Island (New York state).
Prevention: same as lyme disease
Transmission
The main way is through the bite of an infected tick: Babesia microti is spread by Ixodes scapularis ticks, which are commonly called blacklegged ticks or deer ticks. (Although white-tailed deer are the most important food source for the adult stage of the tick, deer are not infected with B. microti.) The parasite typically is spread by the young nymph stage of the tick. Nymphs are mostly found during warm months (spring and summer) in areas with woods, brush, or grass. Infected people might not recall a tick bite because I. scapularis nymphs are very small (about the size of a poppy seed).
Symptoms:
Many people who are infected with Babesia microti feel fine and do not have any symptoms. Some people develop flu-like symptoms, such as fever, chills, sweats, headache, body aches, loss of appetite, nausea, or fatigue. Because Babesia parasites infect red blood cells, babesiosis can cause hemolytic anemia (from the destruction of red blood cells). Babesiosis can be a severe, life-threatening disease, particularly in people who: do not have a spleen; have a weak immune system for other reasons (such as cancer, lymphoma, or AIDS); have other serious health conditions (such as liver or kidney disease); or are elderly.
Treatment
For ill patients, babesiosis usually is treated for at least 7-10 days with a combination of two prescription medications — typically either: atovaquone PLUS azithromycin; OR clindamycin PLUS quinine (this combination is the standard of care for severely ill patients).
Plague Geographic risk, prevention, transmission, possible symptoms and appropriate referral/triage
Endemic in rural areas in central and southern Africa, central Asia and the Indian subcontinent, the northeastern part of South America, and parts of the southwestern United States.
Prevention
Reduce contact with fleas and potentially infected rodents and other wildlife.
Transmission
Usually through the bite of infected rodent fleas. Less common exposures include handling infected animal tissues (hunters, wildlife personnel), inhalation of infectious droplets from cats or dogs with plague, and rarely, contact with a pneumonic plague patient.
Symptoms
Incubation period is typically 1–6 days. Symptoms and signs of the 3 clinical presentations of plague illness are as follows: Bubonic (most common)—rapid onset of fever; painful, swollen, and tender lymph nodes, usually inguinal, axillary, or cervical Pneumonic—high fever, overwhelming pneumonia, cough, bloody sputum, chills Septicemic—fever, prostration, hemorrhagic or thrombotic phenomena, progressing to acral gangrene
Treatment:
Parenteral antibiotic therapy with streptomycin is the recommended first-line therapy; alternatively, gentamicin or, where treatment is limited to oral therapy, doxycycline can be used.
