The Relationship Between Infection Levels and Polymorphisms

Published: 2017-09-12 01:35:03
1558 words
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University of California, Santa Barbara
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The human schistosomiasis original name was bilharzia, named after Theodore Bilharz, who was the first to report the disease in Cairo, Egypt 1851, schistosomiasisis a parasitic disease in people caused by five different species of blood flukes of genus Schistosoma that belongs to class Trematoda. Schistosomiasis is an ancient disease whose eggs have been found in Egypt and Chinese mummies dating back thousands of years (Marquet, S., Abel, L., Hillaire, D., & Dessein, A., 1999). In 1847 a group of Japanese workers (70) described Katayama syndrome (acute schistosomiasis). Schistosoma mansoniSchistosoma haematobium, or Schistosoma japonicum, are major causes of human schistosomiasis while Schistosoma intercalatum and Schistosoma mekongi can affect humans, however, are much less prevailing. S.mekongi, S. japonicum, S. intercalatum and S. mansoni reside in the mesenteric venules as adult worms, while S. heamatobium adults live in the venous plexus surrounding the urinary bladder. Over 200 million persons experience the effect of schistosomiasis globally. However, it majorly resides in tropical regions of Africa, other cases still in China, the Philippines, the Middle East, South America and Caribbean. Schistosoma mansoni is one of the prevalent infecting species of genes infecting more than 83 million human beings (Henri, S., Chevillard, C., Mergani, A., Paris, P., Gaudart, J., Camilla, C., & Magzoub, M., 2002). Research proves that in between ten percent to five percent those infected with schistosomiasis develop the life-threatening symptoms of the disease, while tens of millions suffer understated morbidity.

Polymorphism in biology is the process whereby two or more different morphs or forms occur. Polymorphism is also referred to as phenotypes in the society of species. Polymorphism can be experienced in some ways. A true polymorphic species has individuals significantly of different appearance living in the same locality. Armies of ants always have different sizes of workers yet live in the same net hence are considered to be a polymorphism. Polymorphism is seen as universal in nature; it is related to genetic variation, adoption, and biodiversity. It usually functions to preserve diversification of form in a population living in a varied environment. Most of the typical examples are mimetic forms of butterflies, sexual dimorphism which occurs in many organs and human blood types and hemoglobin.

Prevalence and intensity of schistosomiasis

Schistosomiasis is among the persistent and abandoned tropical illness affecting the poor rural people (Cooke, S., & Hill, 2001). Without proper medication, the disease can lead to anemia or retain the growth of a child, cognitive function, and physical activity. A study was conducted to evaluate the effects of Schistosoma mansoni to individuals subject in different geographical areas. According to the methods used and results collected; populations of 1073 people (545 females and 528 males) were permitted for the research. The ages of the researchers was ranging between 5 to 60 years and a mean of 11 years in Area 1, 24 years in Area 2 and 22 years in Area 3. Results were later inspected using Kato-Kaz method. From the study, the results showed that effects of Schistosoma mansoni infection among the researchers in Area 1, Area 2 and Area 3 was 31.6%, 89.6%, and 59.9% respectively.

The belief that immunity is a major factor controlling the prevalence and strength of schistosomiasis in man is a deep seated one. It is nonviable to most observers that subjects in endemic areas who are exposed to infested waters are not continually reinfected. Additionally, there is a continuous flow of anecdotal evidence for the infectivity of the parasite according to reports generated by individuals from no endemic areas who became infected (in some cases, heavily) after being exposed for only a short duration of time. Despite the fact that the worms dont multiply in the human body, their ability to live for many years ranging from 20 years to 30 years suggests that the burden of the infection should steadily increase to a level in severe mortality and morbidity. In most endemic areas of the world, detection of the disease is relatively little and death due to schistosomal infection. When examining the curve of prevalence and power of infection to age, it reaches its peak in the teens and declines with advancing years. 

The occurrence of immunity to schistosomiasis in man is not a patent phenomenon. Smithers stated that there is no sudden immunologic crisis leading to parasite elimination and a subsequent and immediate development of healthy immunity. Instead, resistance appears to develop gradually, taking several years to become pronounced: in early stages of infection, immunity may be only partial, but nevertheless of significant importance in limiting disease [2]. Attempts to study human resistance to reinfection has been few because of the chronic nature of illness, lack of effective, nontoxic drugs for its elimination and pathogenicity. Innumerable experiments in laboratory animals remain equivocal. All the above impressions and indirect and marginal evidence might suffice to validate the existence of immunity if there were no adequate alternatives to enlighten the fact that most individuals in endemic areas do not develop overwhelming schistosomal infections. A basic degree of protection against the development of massive worm burdens may, however, be related to the biological characteristics of the schistosomes and be afforded by many sociologic and even ecologic factors.

From the same topic, this article also reflects another case study research conducted in the sub-African country in Senegal. The primary goal of the survey was to find out the prevalence and intensity of urinary schistosomiasis among children in school. Urinary schistosomiasis is one of the major threats to the public health in Senegal whereby it is said it exists in all the parts of the country. The total number of schoolchildren enrolled for this research was 210 whose ages ranged in between 7 to 15 years. Standard urine filtration technique was used to examine the presence of Schistosoma haematobium eggs. The results collected showed that 121(57.6%) children were infected with the parasite having a mean of 185 eggs per 10 ml of urine. The presence of the Schistosoma haematobium was found to be present in all the villages that were surveyed in the country. The prevalence statistics suggested that the range was between 14.3% to 92.8%. The rate of infection increased corresponding to increase in age with the highest number was recorded in boys. Research by Briand and Watier (2005) conclude that most endemic area for Schistosoma discovered was Niakhar district which calls for a control program to curb the high rate of infection for better health in the community.

(Hill, A. & V., 2010) supports that there has been widespread of urinary schistosomiasis in most parts of Senegal. The spread of the disease has posed a threat to public health more so among children. It is believed to conquer almost every region with a prevalence of about 25% according to the 2003 record. Niakhar is the leading district with the rate of infection being at 67% since no mass treatment against helminthiasis had been carried out. The study was conducted in Niakhar area in Senegal. The district has a total of 43,000 people distributed all over the 30 villages. The survey mapped all the waters in the region had proved that three-quarter of the population had no any access to a tap water. The National Ethics Committee of Senegal approved the research to be conducted in Niakhar District. The study took place in 2009, 29 of February, June. Cluster sampling was the methodology which is recommended by the World Health Organization.

Out of the total number of 210 urine samples collected, after a very keen examination for S. haematobium, it was found that 57.6% were infected. Averagely it was found that out of 185 of eggs per 10 ml of urine only 72.8% of urine samples which were infected exceeded 49 eggs per 10 ml of urine. Another area of focus was the rate and intensity of S. haematobium infection about access to tap water and water contact. The people who had access to backwater recorded the highest number of disease when compared to individuals who had contact with pond waters. On the other hand, the number of eggs against 10 ml of urine was recorded highly in the people who used lake waters together with who did not have access to tap water. If villages that had access to tap water were considered then, the rate of infection was higher in boys than in girls. Another challenging record noted was the speed of disease was little between the ages of 10 to 12 but after attaining the age of 13 to 15 the prevalence and intensity of infection increased significantly.

Referring to M., Wong and Fish (2003) Niakhar district in Senegal is prone to and endemic for urinary Schistosomiasis. The rate and impact of S.haematobium infection suggested that the Niakhar district community was at a high risk according to Wolrld Health Oorganization (WHO). Out of the total population only 5.5% of the children had received treatment for the parasite hence explains this statistics. The majority of people living in Niakhar district are in rural villages whose lives rely on pond and backwater for bathing, swimming, fishing and any other domestic use. Their water being natural, provide habitat to intermediate hosts and the schistosome parasites. It is given that the waters are the transmission media for the S. haematobium in the community and throughout the entire district. The community living in such a condition is proof that they will continue to be infected and re-infected if no implementation of the strategy to intervene is put in place. The research showed that Niakhar district is an endemic area for urinary schistosomiasis hence the need for health awareness to schoolchildren and the need to provide piped waters to the community.


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