In Summary...
What We Know:
Toxoplasmosis continues to be one of the most commonly overlooked parasites capable of inhabiting the human body, in both developed and developing countries. The CDC estimates that around 60 million people in the United States alone could be infected with Toxoplasma gondii [1]. Even worse, most people don't know they have it. The infection can remain asymptomatic in the body for years before the host becomes aware. Symptoms can display themselves as "flu-like".
People with weakened immune systems are unfortunately most likely to be infected with T. gondii, as well as infants born to mothers who had recently been infected [1]. Luckily, this parasite can't be transmitted from person to person, either directly or indirectly. The only modes of transmission to humans is from cats, via their feces or ingestion of tissue cysts present in meat [8]. Once it has infected a human, it's reached its end. The mortality of T. gondii is relatively low; only the most severe cases, such as infections transmitted in utero, run the risk of life-threatening complications [3].
Fortunately (due to extensive research/study) much is known about the parasite Toxoplasma gondii. The CDC's website provides a detailed list of infection prevention, ranging from thoroughly cooking your meat, washing your vegetables and hands, wearing gloves while gardening, and properly maintaining your cat's litter box.
Toxoplasmosis continues to be one of the most commonly overlooked parasites capable of inhabiting the human body, in both developed and developing countries. The CDC estimates that around 60 million people in the United States alone could be infected with Toxoplasma gondii [1]. Even worse, most people don't know they have it. The infection can remain asymptomatic in the body for years before the host becomes aware. Symptoms can display themselves as "flu-like".
People with weakened immune systems are unfortunately most likely to be infected with T. gondii, as well as infants born to mothers who had recently been infected [1]. Luckily, this parasite can't be transmitted from person to person, either directly or indirectly. The only modes of transmission to humans is from cats, via their feces or ingestion of tissue cysts present in meat [8]. Once it has infected a human, it's reached its end. The mortality of T. gondii is relatively low; only the most severe cases, such as infections transmitted in utero, run the risk of life-threatening complications [3].
Fortunately (due to extensive research/study) much is known about the parasite Toxoplasma gondii. The CDC's website provides a detailed list of infection prevention, ranging from thoroughly cooking your meat, washing your vegetables and hands, wearing gloves while gardening, and properly maintaining your cat's litter box.
Future Directions:
The most important remaining factor about toxoplasmosis is finding a cure. Researchers are still looking into several options for developing a vaccine that would establish immunity in humans. No definitive cure for Toxoplasma gondii infections has yet been developed, additionally treatments for infected individuals (specifically those with weakened immune systems and pregnant women/fetuses) are varying in their degrees of effectiveness in combating the parasite. While the parasite can remain within the individual for their life, diagnostic testing has been developed to determine the infection status of a person, and even if their child (in the case of congenital transmission) has contracted the illness. These diagnostic tests are continually being improved upon, and can identify T. gondii during the various phases of its lifecycle. Serological analysis (antibody levels) along with serum analysis (from blood, tissue, amniotic fluid) can accurately determine if an individual has been, or currently is infected with Toxoplasma gondii [1].
The most important remaining factor about toxoplasmosis is finding a cure. Researchers are still looking into several options for developing a vaccine that would establish immunity in humans. No definitive cure for Toxoplasma gondii infections has yet been developed, additionally treatments for infected individuals (specifically those with weakened immune systems and pregnant women/fetuses) are varying in their degrees of effectiveness in combating the parasite. While the parasite can remain within the individual for their life, diagnostic testing has been developed to determine the infection status of a person, and even if their child (in the case of congenital transmission) has contracted the illness. These diagnostic tests are continually being improved upon, and can identify T. gondii during the various phases of its lifecycle. Serological analysis (antibody levels) along with serum analysis (from blood, tissue, amniotic fluid) can accurately determine if an individual has been, or currently is infected with Toxoplasma gondii [1].
In addition to continued research into toxoplasmosis prevention and treatment, future efforts in fighting this disease should focus on social/public health awareness and monitoring of the parasite. Greater awareness of this parasite will be needed to effectively combat its spread, specifically in countries with a high prevalence on infected cats/persons (ex: Brazil). Education focused towards the transmission and risks associated with toxoplasmosis (regular and congenital) will need to be pursued in terms of the general public to increase awareness. In one study undertaken between 2007-2008 in the Brazilian city of Divinopolis, 93% of surveyed women had little to no knowledge of toxoplasmosis (Figure 18), although South American has some of the highest prevalence of the disease in the world.
Figure 18 Graph depicting the level of knowledge of Toxoplasmosis in pregnant women visiting health clinics in the city of Divinopolis, Brazil. Analysis shows that a strikingly large portion of pregnant women know little to nothing about this disease, which is concerning given the higher prevalence of the parasite in South America, and particularly Brazil where prevalence is estimated to be >60% (see Figure 1).
While eliminating Toxoplasma gondii within both humans and animal hosts may be impossible, an increase in research and public health efforts are needed within the near future to combat this disease around the world. Development of new treatments and diagnostic tests will prove to be just as important as preventative efforts (public education, sanitation, etc.) in decreasing the occurrence and spread of toxoplasmosis within populations around the world. Focus should be given not only to countries which exhibit high prevalence rates of the parasite, but also to at-risk populations (pregnant women, AIDS patients) who may come in contact with the parasite and develop complications as a result.
Further Research
Scientists are still trying to come up with a solution that would decrease the incidence and prevalence of Toxoplasma gondii. A vaccine would be ideal, but due to the complexity of the parasite, it remains improbable for now. The vaccine would need to target selective antigens for all three stages of its lifecycle [4]. Since this parasite is very successful in infecting a wide range of hosts, more than one vaccine would need to be made.
There has been one vaccine, Toxovax, that has shown some benefits. While originally developed to be used in sheep, researchers who introduced it to cats saw an inhibition of the sexual development of T. gondii. This live vaccine has proven to create a level of immunity in cats, but is ineffective in humans [4].
Some researchers are looking into the possibility of developing a genetically engineered vaccine. The idea of a DNA vaccine seems more promising because of their flexibility, rapid manufacture time, and low cost. However, safety is the biggest issue standing in the way of this. Inoculation of these vaccines could potentially elicit immune tolerance, allergic reactions, and production of anti-DNA autoantibodies [4]. Having anti-DNA autoantibodies is a key feature of systemic autoimmune diseases, such as systemic lupus erythematosus. Fortunately this is a rare occurrence [1]. |
Figure 19 Toxovax is the only currently in-use vaccination used to fight Toxoplasma gondii in animals
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