Toxoplasma Gondii - Case Study Example

Contents Contents 2 Introduction 3 Transmission 6 Life cycle 7 Figure cat acts as a definitive host and mice as the intermediate host: the sexual stage takes place in the definitive host whereas the asexual stage takes place in the intermediate host. Furthermore, there are vertical and horizontal transmissions. 9 Current approaches to control or treatment 10 Conclusion: 11 Reference 12 Abstract Toxoplasma gondii is one of the most important zoonotic diseases that could be fatal particularly in immunocompromised patients. Zoonotic diseases are those diseases that are transmitted from animals to humans. Cats act as definitive hosts while humans and other warm-blooded animals act as intermediate hosts. The disease takes various routes of transmission that include vertical and horizontal transmission. The life cycle is divided into two stages; sexual cure in definitive host and asexual, which occurs in the intermediate host. Currently, there is no effective treatment particularly for immunocompromised patients. Study suggests that health education can reduce the burden caused by this disease; other treatment options such as therapeutic agents can also help. There is no vaccination especially for humans. The prepare a four page essay which describes the importance of the disease basic lifecycle or transmission cycle details, the current status of the disease and current approaches to control/treatment. Introduction Toxoplasma gondii is an obligate intracellular parasite (Aspinall et al., 2002), which belongs to protozoan phylum that mainly characterized by the present of apical complex. In addition, “apicomplexa contain a polarized cell structure and two unique apical secretory organelles named micronemes and rhopteries” (Munoz et al., 2011). In general, parasites that belong to the protozoan phylum apicomplexa are said to be responsible for diseases such as malaria, toxoplasmosis and cryptosporidiosis; each of these diseases cause a significantly high rate of mortality and morbidity especially in economically underdeveloped regions of the world (Vedadi et al., 2007). Toxoplasma gondii is one of the world’s most successful parasitic zoonosis, which is transmitted from animal to human. Furthermore, this parasite has the capacity to infect any type of warm-blooded animal including a human being. In addition, it is estimated that it infects between 30% and 70% of the human population (Aspinall et al., 2002; Stocka et al., 2014). According to research, people who suffer from congenital infections, pharmacologically-immunosuppressed patients, and pregnant women have a higher possibility of being infected as compared to other healthy individuals. Moreover, it is approximated that nearly 25% late AIDS patients are developed toxoplasmic encephalitis (Aspinall et al., (2002). Although discovered in 1908, T.gondii’s actual life cycle was understood fully in 1970. It incorporated two key stages, sexual and asexual stages (Dubey, 2009). The definitive host is a cat and the intermediate host is a mouse (see figure 1); humans and other animals such as sheep can be infected by accident either by drinking or by eating contaminated food or water. Contaminated food and water may hold oocysts from cat faeces while undercooked meat may contain cysts tissues. This zoonotic disease is prevalent in most areas of the world, which is a veterinary and medical importance. This is largely due to serious consequences of the illness such as abortion and congenital disease in its intermediated hosts (Dubey, 1998; Tenter et al., 2000). Due to the fact that the apicomplexa disease lacks effective treatment, recent study suggested that urgent treatment or vaccination ought to be developed. The object of this essay This essay will consider the life cycle of toxoplasma gondii, the main transmission methods such as congenital, carnivorism, and faecal oral, current treatment, and develop new ways to create an effective treatment or vaccination. Transmission Toxoplasma gondii has developed several potential routes of transmission. Firstly, it may be transmitted vertically by tachyzoites that invade host cells and replicate quickly by “endogeny that leads subsequently to lysis of the infected cell and spread to neighbouring cells” (Munoz et al., 2011). This implies that it can be passed to the foetus via the placenta during pregnancy. According to research, the first congenital transmission case was identified in 1938 where an infant girl was developing “convulsive seizures at 3 days of age and lesions were noted in the maculae of both eyes through an ophthalmoscope” and passed away at the age of one month (Dubey, 2009). In addition, the same transmission applies to animals such as rodents but is very common in sheep (Dubey, 2009). Secondly, horizontal transmission of T. gondii can also take place and involves three life-cycle stages. This transmission can take place through ingestion of infectious oocysts from the environment, ingestion of tissue cysts, and through tachyzoites, which are commonly found in meat such as pig, chicken, and lambs. These infectious meat products result from tissue cysts, which can then be consumed by humans. Other transmissions can occur in tissue transplants or unpasteurised milk and in transferred blood, which contains the infection stage known as tachyzoites. (Hill and Dubey., 2013; Tenter et al., 2000). In the past, consumption of either raw or undercooked meat, especially that of sheep and pigs, had been regarded as a key route of transmission to human beings. This implies that different cultures and eating habits may lead to different transmission outcomes (Tenter et al., 2000). However, according to recent study, there is no clear evidence indicating whether these routes are the most important in epidemiology. Furthermore, recent outbreaks in America indicate that acute toxoplasmoses in humans are largely associated with oocyst contamination of the environment. Therefore, the transmission could be largely associated with the oocysts that could be potential sources of infection for humans. Effective methods to monitor these issues are currently being developed (Hill and Dubey, 2013). Life cycle According to research, T. gondii is facultatively heteroxeno (figure 2). The definitive hosts are members of the Felidae family such as domestic cats. On the other hand, the intermediate hosts include sheep, mice, and humans that can be infected through ingestion of oocyst from a cat’s faeces (Tenter et al., 2000). The life cycle of Toxoplasma gondii is complex. This is mostly due to the involvement of sexual as well as asexual multiplication (Munoz et al., 2011). The sexual stage takes place in the definitive host where the parasite replicates in the intestine of the definitive host leading to the production of oocysts that are in turn passed through the cat’s faeces. The ooocysts then undergo sporulation. Subsequently, when the intermediate host ingests the infected oocysts, either through water or through contaminated food, the two phases of asexual development take place. The first phase is known as tachyzoites or endozoites where it multiplies rapidly through repeated endodyogeny in various host cells and eventually encysts in several tissues. This takes place in the brain and tissue cysts, which persist for a long time (Dubey, 1998). The second phase, as initiated by the previous generation of tachyzoites, is prompted by the formation and development of tissue cysts within the tissue cyst bradyzoites. It multiplies slowly through endodygeny giving rise to the tachyzoite that can infect virtually any cell in the body. Therefore, “If a host is primarily infected during pregnancy, tachyzoites may be transmitted transplacentally to the foetus” (Opsteegh et al., 2013). Furthermore, it divides by a specialized process called endodyogeny that was identified after studying ultrastructure of the tachyzoite, which helps in providing a complete description of endodyogeny since they fully describe its ultrastructure. When a cat ingests prey animal or meat infected with a T. gondii, bradyzoites are released from the cysts tissue contained in their meal and complete its life cycle (Sheffield and Melton 1968; Munoz et al., 2011; Dubey, 2014; Opsteegh et al., 2013). Figure 1; cat acts as a definitive host and mice as the intermediate host: the sexual stage takes place in the definitive host whereas the asexual stage takes place in the intermediate host. Furthermore, there are vertical and horizontal transmissions. Current approaches to control or treatment It is commonly known that there is no effective treatment especially for immunocompromised patients such as those suffering from AIDS. However, according to recent study, sulphonamides are used as an effective way of guarding against murine toxoplasmosis (Dubey, 2014). Furthermore, standard therapeutic agents are used for the treatment of toxoplasmosis, which is usually a combination such as pyrimethamine and sulphadiazine (Dubey, 2014; McLeod et al., 2014). The burden of this disease has been reduced significantly especially through usage of preventive measures, which can be divided into two categories. Firstly, health education usually aimed for pregnant women and immunocompromised patient. According to recent study, temperatures required to kill T.gondii in infected meat can be realized through freezing of meat overnight and cooking the meat well. In addition, washing of vegetables and fruit well is recommended. However, some studies have argued that the prevention measures should also target the general population through health education to the total population (Opsteegh et al., 2013; Ferguson, 2009). Secondly, serologic screening test is used during pregnancy to prevent the transmission of T.gondii to foetus. Furthermore, pregnant women with seropositive prevent transmission of infection to foetus through treatment with spiramycin. This implies that these screening programmes have been effective in passing information regarding prevention of toxoplasmosis. However, these screening methods are costly especially if majority of women are seronegative, as they require follow up during pregnancy. Studies have also suggested that vaccination of sheep can help in reducing neonatal mortality in lambs. This type of vaccination is available only for sheep. On the other hand, human beings do not have vaccination. Therefore, research should manly focus on developing vaccination to help in preventing transmission of the infection. Conclusion: T.gondii is the most important zoonotic disease that is transmitted from animal to human. In addition, it causes life-threating situations especially to immunocompromised patients and pregnant women as it can cause abortion and other acute illness. This disease has different transmission routes but, according to recent study, oocyst is the main route of transmission that can be found in the definitive host faeces. The infected faeces can in turn be transmitted through contaminated food or water. Direct contamination can also occur with an infected cat. The life cycle consists of two stages that incorporate sexual in definitive host and asexual in intermediate host. There are several types of treatment that can be applied although, currently, there is no effective treatment available especially to immunocompromised patients. Furthermore, health education is one of the most important prevention procedures, as it raises public awareness on ways of avoiding transmission especially in pregnant women. However, recent study has suggested that vaccination need to be developed to prevent the transmission of the disease. Reference Aspinall, T. V., Marlee, D., Hyde, J. E. & Sims, P. F. (2002). 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