Toxoplasmosis. Betty Bowles, RN, MSN, Nelda Coleman, RN, MSN, Lauren Jansen, RN, MSN. Midwestern State University

Transcription

1 Toxoplasmosis 1 Running Head: TOXOPLASMOSIS Toxoplasmosis Betty Bowles, RN, MSN, Nelda Coleman, RN, MSN, Lauren Jansen, RN, MSN Midwestern State University

2 Toxoplasmosis 2 Abstract Toxoplasmosis is a disease caused by infection with the protozoan parasite Toxoplasma gondii. It has worldwide distribution. Cats are its definitive hosts and excrete oocysts in their feces. Other hosts, including humans, are infected by ingesting contaminated food or drink or undercooked contaminated meat. Acquired infection of immunocompetent persons is usually asymptomatic. Occasional symptomatic infection is usually benign and self limited. However, the disease can have devastating consequences in immunodeficient and congentitally infected individuals.

3 Toxoplasmosis 3 Toxoplasmosis History and Causative Agent The causative agent for Toxoplasmosis is toxoplasma gondii. T gondii is an intracellular protozoan parasite of warm blooded animals. According to Sciammarella (2002), it is one of the most common human parasites in the world. Toxoplasmosis was first described by Nicolle and Manceaux in 1908 from their observations of parasites in the blood, liver and spleen of the gundi, a North African rodent, or Ctenodactylus gondii. In 1909, the parasite was named toxoplasma because of its bow or arc shape and gondii for the rodent from which it was recovered (Hoklek & Safdar, 2004). In 1923, while studying an infant who had hydrocephalus, seizures, and ocular anomalies, Janku discovered parasitic cysts on the retina (Hoklek & Safdar, 2004). Wolf and Cowan (1937) established T. gondii as a potential cause of human neonatal encephalitis. Subsequently Paige, Cowen and Wolf (1942) determined that toxoplasmosis could be congenitally acquired. Following that finding, there was a great deal of interest in toxoplasmosis that was interrupted during the war. With the development of precise serologic diagnostic procedures in 1948, toxoplasmosis infections in animals and humans have gotten renewed attention and become a world-wide concern (Feldman, 1958). T gondii has three forms: sporozoites present in oocysts; tachyzoites which invade and replicate within cells during the acute stage; and bradyzoites present in tissue cysts during the latent stage (CDC, 2000). T gondii also has two distinct life cycles. The definitive host is the cat in which the sexual cycle occurs. The asexual cycle can occur in other mammals including humans and in certain bird species. Cats can become infected by ingesting oocysts from cat feces or tissue cysts from eating the flesh of animals such

4 Toxoplasmosis 4 as birds or rodents. Digestive enzymes release the organisms which reproduce to form zygotes that become encapsulated, noninfectious oocysts that are excreted in their feces. During a primary infection, the cat sheds millions of oocysts daily for several weeks. Within 21 days of excretion the oocysts become infectious. These oocysts are very hardy and can remain viable in warm, humid environments for a year or more (Sciammarella, 2002). The second form of T gondii is the tachyzoites which actively proliferate and can be present in any organ during the acute stage of infection. They commonly invade the brain, skeletal muscle and heart muscle. The infection continues until the cells die or a tissue cyst forms. The bradyzoites, the third form of the T gondii, form tissue cysts as early as seven days after infection and remain for the lifespan of the host. Tissue cysts are seen during the chronic or latent stage of infection. They can contribute to transmission if these tissues are ingested by carnivores. After ingestion, the cysts are broken down by digestive enzymes causing them to release the organism to invade the gastrointestinal tract where it can spread through the blood and lymphatic circulation (Sciammarella, 2002). Historical Outbreaks / Epidemics Since toxoplasmosis is not a nationally reportable disease in the United States the most reliable information about the incidence in the general population has been derived from serosurveys which determine the percentage of persons with elevated Toxoplasmaspecific IgG antibodies. According to Lopez, Dietze, Wilson, Navin and Jones (2000) the rates of infection with Toxoplasma in the United States appears to be declining. A study of military recruits in the 1960s reported an overall seroprevalence of 14% (Feldman,

5 Toxoplasmosis ). A second study of military recruits in 1989 indicated a reduction in seroprevalence to 9.6% (Smith, Wilson & Hightower, 1996). Downward trends have also been observed in France (Jeannel, et al, 1988) and Sweden (Forsgren et al, 1991). More recent data from the third National Health and Nutrition Examination Survey (NHANES III) conducted from , which tested 17,658 persons for Toxmoplasma-specific IgG antibodies found 23% to be positive (Guerina, Hsu & Meissner, 1994). While serosurveys can help to define trends in seropositivity rates in the general population, they are not helpful in estimating the prevalence of congenital toxoplasmosis. Two prospective studies in the 1970s reported congenital toxoplasmosis rates ranging from 7 per 10,000 live births in New York (Kimball, Kean & Fuchs, 1971) to 13 per 10,000 live births in Alabama (Alford, Stagno & Reynolds, 1974). Infant testing from by the New England Regional Newborn Screening Program reported an infection rate of only 1 per 10,000 (Guerina, N.G., Hsu, H. & Meisner, H, 1994). Moura, et al. (2002) reported the world s largest outbreak of water-borne toxoplasmosis. T. gondii was isolated from municipal reservoirs and household storage tanks in a small city in Brazil following an outbreak of 600 acute cases of which 8% exhibited ocular toxoplasmosis. Of the total cases, 7 were pregnant with 1 miscarrying and 5 delivering seropositive infants. The suspected source of infection was a cat that lived on and delivered seropositive kittens on the top of the implicated reservoir. A ProMED-mail search from yielded several alerts related to toxoplasmosis, in addition to the Brazilian outbreak discussed above (ProMED-mail, 2002). In 1992, 20 people in Brazil fell ill after eating contaminated mutton (ProMED-mail, 2002). In 1995 there was an outbreak of 35 cases in British Columbia believed to be related to infected

6 Toxoplasmosis 6 foods (ProMED-mail, 1995a), and 12 cases in Australia believed to be caused by their cat plague and by eating undercooked kangaroo meat (ProMED-mail, 1995b). Animal outbreaks were reported in Australia when 50% of sheep aborted toxoplasma-infected lambs in 2004 (ProMED-mail, 2004a). That same year 4 of 5 toxoplasma-infected kangaroos in an Indiana zoo died (ProMED-mail, 2004b). Another outbreak in sheep in Australia in 2005 renewed concern for the increasing feral cat population (ProMED-mail, 2005a). Isolated cases of an infected peregrine in Australia (ProMED-mail, 1996). and an infected sea otter in Alaska (ProMED-mail, 2005b) were also reported. Modes of Transmission Animals or humans become infected by ingesting oocysts from cat feces or tissue cysts from contaminated meat (see Figure 1). Infection occurs by ingestion of the oocysts after handling contaminated soil or cat litter or by consuming contaminated water or foods such as unwashed garden vegetables. Touching unwashed hands to the mouth after gardening or changing the cat litter can cause infection. Children can become infected by playing in dirt piles or sand boxes contaminated by infected cats. Ingestion of tissue cysts occurs when infected meat is eaten raw or undercooked. According to Hokelek (2004), in many parts of the world, 5-35% of pork, 9-60% of lamb, and up to 9% of beef contain T gondii. Wild game is often infected with the highest prevalence in black bears and white-tailed deer. Virtually all edible portions of an animal can harbor viable T gondii organisms. It can also be transmitted by containers, knives or other utensils, cutting boards or other preparation surfaces contaminated with raw meat. Touching unwashed hands to the face after meat preparation is another source of infection. According to the American Academy of Family Physicians (2005) oocysts can

7 Toxoplasmosis 7 also be transported to food by flies, cockroaches or other insects, or by ingestion of unpasteurized milk and raw eggs. Human to human transmission is possible. Toxoplasmosis can be transmitted transplacentally from an infected mother to her fetus. According to the CDC (2005) there are no studies at this time documenting breastmilk transmission. The CDC recommends that women who contract the disease during pregnancy should breastfeed. Rare human to human transmission can occur by transplantation of infected organs, through blood transfusion or because of laboratory accidents (Sciammarella, 2002; Hoklek and Safdar, 2004). Symptoms of Toxoplasmosis In most immunocompetent persons infection with Toxoplasma is asymptomatic. Others may exhibit flu-like symptoms like lymphadenopathy, fever, malaise, night sweats or muscle aches and pains (Hokelek & Safdar, 2004). Other symptoms include stiff neck, headache, fatigue, anorexia, arthralgia, rash, sore throat or headache. Less common symptoms include confusion, earache, nausea, eye pain and abdominal pain (Hill & Dubey, 2002). These symptoms can last for a month or more. Severe toxoplasmosis, which causes damage to the brain, eyes, or other organs can occur with an acute infection or reactivate from an earlier infection. This usually occurs in immunocompromised persons such as those with Acquired Immunodeficiency Syndrome (AIDS), those receiving chemotherapy, or organ transplant recipients on immunosuppressive drugs. Encephalitis is the important manifestation in these persons with symptoms of headache, disorientation, drowsiness, hemiparesis, reflex changes, convulsions and coma. Toxoplasmosis is a common cause of death in AIDS patients..

8 Toxoplasmosis 8 While the brain is the most frequently affected organ, toxoplasmosis can involve any organ including the testis, dermis and spinal cord (Hill & Dubrey, 2002). Women who acquire Toxoplasmosis during pregnancy rarely have symptoms other than temporary parasitemia. Congenitally infected infants may have a wide spectrum of clinical diseases. While most infants infected in utero are born with no obvious signs on routine newborn examination, up to 80% develop learning or visual disabilities later in life. Mild disease may consist of slightly diminished vision, whereas more severe cases may have retinochoroiditis, hydrocephalus, convulsions and intracerebral calcification. The least common but most dramatic sequel is hydrocephalus. The most common sequel is ocular disease. Symptoms of congenital toxoplasmosis may include fever, lymphadenopathy, jaundice, unusually large or small head, maculopapular rash, bruises or bleeding under the skin, anemia and enlarged liver and spleen. With brain or nervous system anomalies symptoms may include seizures, poor muscle tone, spasticity and palsies, feeding difficulties, hearing loss and mental retardation. Severe vision problems or blindness can occur with eye involvement (KidsHealth, 2005). Precautions to Prevent Toxoplasmosis According to the CDC Fact Sheet (2004), there are several sanitation and food steps individuals can take to reduce their chances of becoming infected with Toxoplasmosis. When gardening or doing anything that involves the handling of soil, wear gloves. Always wash your hands thoroughly with soap and water after any outdoor activities. The CDC Fact Sheet reports that individuals should wash their hands after handling raw meat. Cutting boards, sinks, knives and other utensils that have come in contact with the raw meat should be cleaned with soap and hot water. Meat needs to be

9 Toxoplasmosis 9 cooked thoroughly to an internal temperature of 160 degrees or until the center is no longer pink and the juices or colorless. Meat should not be consumed before it is fully cooked. Fly and roach control measures can be implemented to prevent contamination of foods by these routes. The Mayo Clinic Toxoplasmosis (2005) recommends washing all fruits and vegetables before consumption. Avoid drinking unpasteurized goat s milk since toxoplasma parasites may be present. House cats should be kept indoors and fed dry or canned cat food, and not raw meat. According to the Mayo Clinic, do not adopt kittens or cats since it takes over a month to get the results back from having the animal tested for toxoplasmosis. They also recommend wearing gloves when emptying the cat litter box. Cleaning the litter box daily prevents any excreted oocysts from having time to become infectious. The litter box should be disinfected with boiling water since chemical disinfectants are not effective against T. gondii. Lihteh (2005) reports that contaminated water should not be consumed since it has been reported to cause and outbreak of toxoplasmosis. According to Jones, Lopez and Wilson (2003) most instances of Toxoplasmosis can be prevented through education. Logar et al. (2002) recommend that a pregnant woman should be tested at least three times throughout the pregnancy to ensure that the toxoplasmosis is not missed. They contend that serological screening during pregnancy combined with health education justifies the costs of disease prevention. The CDC (2002) recommends health education that is directed to all women of childbearing age on soil-borne and meat-related toxoplasmosis prevention. They also suggest that pregnant women should be educated by

10 Toxoplasmosis 10 healthcare providers on their first prenatal visit about food hygiene and the importance of preventing exposure to cat feces.

11 Toxoplasmosis 11 Effect of the Outbreak on Society Jones, Lopez and Wilson (2003) reports that a recent survey conducted as part of the Third National Health and Nutrition Survey found that 15 percent of women of childbearing age in the United States (U.S.) test positive for the T.gondii infection. A pregnant women infected with T. gondii can cause serious health problems if the infection is transmitted to the fetus. An estimate of 400 to 4,000 cases of congenital toxoplasmosis occurs each year in the U.S. Women who become acutely infected or have a reactivation episode of the infection can transmit the organism tranplacentally. Congenital toxoplasmosis can cause mental retardation, blindness and epilepsy in infancy or occur later in life. Women infected with the parasite before conception rarely transmit the infection to their fetus (Jones, Lopez & Wilson). Infection in early pregnancy can lead to miscarriage or intrauterine fetal death (Hagay & Furman, 2004). Congenital toxoplasmosis is most severe when the mother becomes infected in the first trimester. When the pregnant woman acquires the infection in the first trimester, approximately 10-24% of fetuses are infected and the disease in the infant is usually severe. If the infection is acquired in the third trimester, 60-90% of fetuses are infected, but the disease is mild or asymptomatic at birth (Jones, Lopez & Wilson, 2003). These differences in transmission may be related to placental blood flow, virulence of the organism or the immunocompetence of the mother (Hokelek, 2004). Logar et al. (2002) reports that while congenital toxoplasmosis is a rare disease, it is a worldwide health problem. The incidence of Toxoplasma infection is known to depend on the prevailing climatic conditions, cultural traditions and eating habits of a particular country and it therefore varies from one geographical area to another, even within the same country (p. 201).

12 Toxoplasmosis 12 They go on to report that the overall risk of congenital infection during pregnancy is approximately 20 to 50 percent. Comparison of Toxoplasmosis to Aids According to the Mayo Clinic HIV/AIDS (2005), AIDS is caused by the human immunodeficiency virus (HIV). It is a life-threatening disease that interferes with the body s ability to fight off bacteria, viruses and fungi that cause diseases. Mayo Clinic goes on to explain that the virus and the infection are known as HIV and the term AIDS is the end stage of the HIV infection. Logar et al. (2002) states that toxoplasmosis is caused by the parasite Toxoplasma gondii. Toxoplasmosis is a common parasitic infection in humans. The Mayo Clinic HIV/AIDS (2005) reports that the modes of transmission for HIV includes sexual contact, infected blood, shared needles or syringes, and untreated pregnant women with HIV can transmit the infection to their babies during pregnancy, delivery and through breast milk. Jones, Lopez & Wilson (2003) report that T. gondii can be transmitted to humans in three principal routes. They include inadequately cooked infected meat or uncooked foods that have come in contact with infected meat; inadvertently ingesting oocysts; and the infection is transmitted transplacentally from the infected mother to her unborn fetus. It is possible for both infections to be transmitted through organ transplantation or blood transfusion (Montoya & Liesenfeld, 2004, and Mayo Clinic). When infected with toxoplasmosis or AIDS the individual may have no symptoms. It is common to develop flu like symptoms for both diseases. Individuals with compromised immune systems are more prone to contact the disease. (Mayo Clinic

13 Toxoplasmosis 13 HIV/AIDS, 2005 & Mayo Clinic Toxomplasmosis, 2005). According to Mayo Clinic HIV/AIDS, while there has been progress against AIDS there is no vaccine or cure for the disease. Mayo Clinic Toxoplasmosis reports that most healthy individuals do not require any treatment for toxoplasmosis. For individuals who show signs and symptoms of acute toxoplasmosis, the physician may prescribe Pyrimethamine (antimalarial) and Sulfadiazine (antibiotic) medications for treatment. Dormancy or latency for both with active infection occurring later.

14 Toxoplasmosis 14 References American Academy of Family Physicians (2005). Toxoplasmosis in pregnancy. Retrieved September 28, 2005 from CDC Fact Sheet (2005). Toxoplasmosis. Parasitic Disease Information. Retrieved November 16, 2005 from m Centers for Disease Control and Prevention (2005). Breastfeeding: Infectious diseases and specific conditions affecting human milk: Toxoplasmosis. Retrieved November 15, 2005 from Centers for Disease Control and Prevention. CDC Recommendations Regarding Selected Conditions Affecting Women s Health. MMWR 2000; 49(RR-2): Feldman, H. (1958). Toxoplasmosis. American Academy of Pediatric, 22(3). Retrieved November 21, 2005 from Hill, D. & Dubey, J.P. (2002). Toxoplasma gondii: transmission, diagnosis and prevention. European Society of Clinical Microbiology and Infectious Diseases, 8: Hoklek, M. and Safdar, A. (2004). Toxoplasmosis. Retrieved November 15, 2005 from

15 Toxoplasmosis 15 Jones, J, Lopez, A, and Wilson, M. (2003). Congenital toxoplasmosis. American Family Physician, 67(10), KidsHealth (2005). Toxoplasmosis. Retrieved September 28, 2005 from Lihteh, W. (2005). Toxoplasmosis. E-medicine. Retrieved September 28, 2005 from Logar, J., Petrovec, M., Novak-Antolic, Z., Premru-srsen, T., Cizman, M., Arnez, M., et al. (2002). Prevention of congenital toxoplasmosis in Slovenia by serological screening of pregnant women. Scandinavia Journal of Infectious Diseases, 34, Montoya, J., and Liesenfeld, O. (2004). Toxoplasmosis. The Lancet, 363, Mayo Clinic (2005). HIV/AIDS. Retrieved November 16, 2005 from t& Mayo Clinic (2005). Toxoplasmosis. Retrieved November 16, 2005 from Moura, L, Wada, M., Carmo, E, Dusi, R., Tuboi, S. H., Camargo, N. et al. (2002, April 23). Epidemic of toxoplasmosis associated with ingestion of contaminated municipal water Brazil. Paper presented at the Epidemic Intelligence Service 51 st Annual Conference. Retrieved November 15, 2005 from Paige, B., Cowen, D. and Wolff, A. (1942). Toxoplasmic encephalitis. V. Further

16 Toxoplasmosis 16 observations of infantile toxoplasmosis: visceral manifestation. American Journal of Diseases in Children, 63, ProMED-mail. Toxoplasmosis -Australia. ProMED-mail 1995a; 24 October: Retrieved November 16, 2005 from ProMED-mail. Toxoplasmosis Outbreak in British Columbia, Canada. ProMED-mail 1995b; 15 May: Retrieved November 16, 2005 from ProMED-mail. Toxoplasmosis in a Peregrine -Australia. ProMED-mail 1996; 26 July: Retrieved November 16, 2005 from ProMED-mail. Toxoplasmosis Brazil (Parana). ProMED-mail 2002; 12 January: Retrieved November 16, 2005 from. ProMED-mail. Toxoplasmosis, Sheep Australia (Tasmania). ProMED-mail 2004a; 08 March: Retrieved November 16, 2005 from ProMED-mail. Toxoplasmosis, Zoo Kangaroo USA (Indiana). ProMED-mail 2004b; 23 July: Retrieved November 16, 2005 from ProMED-mail. Toxoplasmosis, Sheep Australia (Tasmania). ProMED-mail 2005a; 25 September: Retrieved November 16, 2005 from ProMED-mail. Toxoplasmosis, Sea Otter USA (Alaska). ProMED-mail 2005; 25 February: Retrieved November 16, 2005 from

17 Toxoplasmosis 17 Sciammarella, J. (2002). Toxoplasmosis. Retrieved September 28, 2005 from Wolf, A., Cowen, D. (1937). Granulomatous encephalomyelitis due to an encephalitozoon (encephalitozoic encephalomyelitis). A new protozoan disease of man. Bulletin of Neurological Institute of New York, 6,

18 Toxoplasmosis 18 Cat fecal oocysts (sexual cycle) Tissue cysts in cat s prey (rodents & birds) Oocysts contaminate cat litter Soil, water & grass contaminated with oocysts Oocysts on unwashed fruits & vegetables Oocysts ingested by animals whose meat then contains tissue cysts Humans ingest oocysts in contaminated soil, cat litter, fruits, vegetables, water or tissue cysts in undercooked meat Transmitted transplacentally to fetus (Congenital Toxoplasmosis) Organ Transplant or Blood Transfusion from infected person Figure 1. Pathways for Toxoplasma gondii transmission. The cat s intestinal track is the only source for production of oocysts. Human infection occurs through ingestion of oocysts from contaminated sources (soil, cat litter, fruits, vegetables, water) or ingestion of tissue cysts in undercooked meat from infected animals. Human to human transmission is transplacental or through contaminated organ transplants or blood transfusions.