Chapter 3Infectious Diseases Related To Travel
Jeffrey L. Jones
Toxoplasma gondii is an intracellular coccidian protozoan parasite of humans and warm-blooded animals that completes the sexual phase of its life cycle in cats.
MODE OF TRANSMISSION
Toxoplasmosis is transmitted by the following:
- Ingestion of oocysts in cat feces or soil or water contaminated with cat feces
- Ingestion of undercooked meat
- Congenitally when a woman becomes infected during pregnancy
- Blood transfusion and organ transplantation
Human infection with T. gondii occurs worldwide. The prevalence in adults ranges from <10% to >90%; higher prevalences tend to occur at lower elevations and in latitudes closer to the equator. The risk for infection is higher in many developing and tropical countries, especially when people eat undercooked meat, drink untreated water, or are extensively exposed to soil.
The incubation period is 5–23 days. Acute infection in children and adults with normal immunity is often asymptomatic. When illness occurs, it is usually mild with influenzalike symptoms (such as tender lymph nodes and muscle aches) that last for several weeks. An infectious mononucleosislike syndrome has been described in febrile returning travelers, characterized by prolonged fever, lymphadenopathy, elevated liver enzymes, lymphocytosis, and weakness. Among acutely infected people, 0.5%–2% develop ocular disease, usually retinochoroiditis; symptoms include blurred vision, pain, photophobia, tearing, and loss of vision. Higher rates of ocular disease have been described in southern Brazil.
In severely immunosuppressed people, including those with HIV infection, severe and even fatal toxoplasmic encephalitis, pneumonitis, and other systemic illnesses can occur, most often from reactivation of a previous infection. Immunosuppressed people with HIV infection are routinely prescribed prophylactic medication active against T. gondii.
In 70%–90% of cases, infants with congenital toxoplasmosis are asymptomatic or have mild symptoms not recognized at birth. However, learning disabilities, mental retardation, or visual impairment often occur later in life. Congenital infection can result in maculopapular rash, generalized lymphadenopathy, hepatomegaly, splenomegaly, jaundice, and thrombocytopenia. In addition, hydrocephalus, microcephaly, seizures, retinochoroiditis, and deafness can occur. Cerebral calcifications may be seen on radiography or ultrasonography of the head.
Acutely infected children and adults are diagnosed by serologic testing for T. gondii antibodies (Toxoplasma-specific IgM and IgG). Ocular disease is diagnosed by characteristic retinal lesions and serum testing for T. gondii antibodies; ocular fluid can also be tested for T. gondii antibodies.
Immunosuppressed people are diagnosed by serologic testing (usually but not always Toxoplasma IgG positive), typical clinical course, and identification of 1 or more mass lesions by CT, MRI, or other radiographic testing. Biopsy may be needed to make a definitive diagnosis.
To determine infection status and help estimate the timing of infection in pregnant women, serologic testing at a Toxoplasma reference laboratory is recommended (for example, IgM, IgG, avidity, and at some laboratories, differential agglutination [AC/HS test], IgA, and IgE). Some commercial IgM tests have high false-positive rates. Fetal and congenital infections often require PCR and reference laboratory assistance for diagnosis.
Pyrimethamine and sulfadiazine are the mainstays of treatment in adults. Ocular disease should be treated in consultation with an ophthalmologist. Corticosteroids may be added to regimens of pyrimethamine, sulfadiazine, and leucovorin (or other combinations of drugs active against T. gondii) when retinochoroiditis threatens vision. Immunosuppressed people with active toxoplasmosis should be treated in consultation with a physician experienced in treating immunosuppressed people. Toxoplasmosis during pregnancy and congenital infection in the infant should be treated in consultation with fetal medicine and pediatric specialists.
PREVENTIVE MEASURES FOR TRAVELERS
Travelers should be advised to do the following:
- Cook meat to safe temperatures (≥160°F [71°C] throughout).
- Peel or wash fruits and vegetables thoroughly before eating.
- Wash cutting boards, dishes, counters, utensils, and hands with hot, soapy water after contact with raw meat or with unwashed fruits or vegetables.
- Freeze meat for several days before cooking to reduce chance of infection.
- Wear gloves when gardening and during any contact with soil or sand, because soil or sand might be contaminated with cat feces that contain T. gondii. Wash hands thoroughly after gardening or contact with soil or sand.
- Avoid drinking untreated water. T. gondii is not killed by chlorine levels used for water treatment, so in developing countries water must be treated and adequately filtered or boiled; alternatively, use safe bottled water.
- Change the litter box daily. T. gondii does not become infectious until 1–5 days after it is shed in a cat’s feces.
Pregnant or immunocompromised people should take the following additional precautions:
- Avoid changing cat litter if possible. If no one else can perform the task, wear disposable gloves and wash hands thoroughly with soap and water afterward.
- Keep cats indoors.
- Do not adopt or handle stray cats, especially kittens. While pregnant, do not get a new cat.
- Feed cats only canned or dried commercial food or well-cooked table food, not raw or undercooked meats.
- Keep outdoor sandboxes covered.
- Abramowicz M. Drugs for Parasitic Infections. New Rochelle (NY): The Medical Letter, Inc; 2007.
- Bottieau E, Clerinx J, Van den Enden E, Van Esbroeck M, Colebunders R, Van Gompel A, et al. Infectious mononucleosis-like syndromes in febrile travelers returning from the tropics. J Travel Med. 2006 Jul–Aug;13(4):191–7.
- CDC. Toxoplasmosis. Atlanta: CDC. Available from: http://www.cdc.gov/toxoplasmosis.
- Kaplan JE, Benson C, Holmes KH, Brooks JT, Pau A, Masur H. Guidelines for prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: recommendations from CDC, the National Institutes of Health, and the HIV Medicine Association of the Infectious Diseases Society of America. MMWR Recomm Rep. 2009 Apr 10;58(RR-4):1–207.
- Montoya JG, Liesenfeld O. Toxoplasmosis. Lancet. 2004 Jun 12;363(9425):1965–76.
- Montoya JG, Remington JS. Management of Toxoplasma gondii infection during pregnancy. Clin Infect Dis. 2008 Aug 15;47(4):554–66.
- Travel Notices
- Find a Clinic
- Disease Directory
- Information Centers
- Traveler Information Center
- Common Travel Health Topics
- Adventure Travel
- Bug Bites
- Business Travel
- Counterfeit Drugs
- Cruise Ship Travel
- Cold Climates
- Deep Vein Thrombosis
- Food and Water
- Health Care Abroad
- High Altitudes
- Hot Climates
- Humanitarian Aid Workers
- Jet Lag
- Last-Minute Travel
- Long-Term Travel
- Mass Gatherings
- Medical Tourism
- Mental Health
- Motion Sickness
- Natural Disasters
- Pregnant Travelers
- Road Safety
- Senior Citizens
- Sex Tourism
- Sick After Travel
- Study Abroad
- Sun Exposure
- Swimming and Diving
- Travelers' Diarrhea
- Travelers with Chronic Illnesses
- Travelers with Weakened Immune Systems
- Traveling with a Disability
- Traveling with Your Pet
- Visiting Friends or Relatives
- Water Disinfection
- Traveler Survival Guide
- CDC-TV Videos
- Common Travel Health Topics
- Clinician Information Center
- Travel Industry Information Center
- Traveler Information Center
- Yellow Book
- RSS Feeds
Before you travel make sure you speak with your doctor.