Schistosomiasis 200 Million People Afflicted

Schistosomiasis

200 MILLION PEOPLE AFFLICTED

Neglected Diseases: Schistosomiasis

Schistosomiasis, also called bilharzia, is a blood fluke infection, which can cause serious and long-term illness (DHPE, 2010; DPDx, 2010; Kogulan & Lucey, 2007; Pearson, 2009). It was first identified by Theodore Bilharz in Egypt in 1851 and, thus, named after him in some countries. Blood flukes, which cause schistosomiasis, are parasitic flatworms, called schistosomes. Schistosomiasis is found in Africa, Latin America, Caribbean, Middle East, Southern China, and Southeast Asia (DHPE, DPDx, Kogulan & Lucey, Pearson).

Main Types and Transmission

The three main types or species, which affect humans, are Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium (DPHE, 2010; DPDx, 2010; Kogulan & Lucey, 2007; Pearson, 2009). The flatworms live and thrive in fresh water in these regions. They must first mature in freshwater snails as intermediate hosts before they can infect human beings. This happens when their eggs are excreted from urine or feces, hatch and release miracidia under favorable conditions. These miracidia swim and penetrate the snails as intermediate hosts. These snails harbor 2 generations of sporocysts and produce infective cercariae. When released, these cercariae swim and penetrate the skin of the human host. Inside the human host, these cercariae eliminate their forked tail and become schistosomulae. They circulate through the tissues in stages until they reach and are deposited in the veins, particularly the mesenteric venules, in different parts, depending on the species or type of worm. Schistosoma japonicum or S. japonicum tends to inhabit the superior mesenteric veins in the small intestines. S. mansoni tends to localize in the large intestines. And S. haematobium is most often found in the bladder. All three types, however, can move between sites and settle in any location. The females of these worms deposit their eggs in the veins of body systems, which progressively move towards the lumen of the intestines, the bladder and the ureters, depending on the specie or type. From there, the eggs are excreted in the feces or urine. The eggs survive in fresh water up to 48 hours. Persons at risk are those who use water for washing or bathing, swimming or as work environment, such as fishing, rice cultivation or irrigation. The growth process of these worms within the human body occurs within several weeks

(DPHE, DPDx, Kogulan & Lucey, Pearson).

Diseases Caused

These worms or blood flukes cause different illnesses, depending on the specie or type (DPHE, 2010; DPDx, 2010; Kogulan & Lucey, 2007). S. mansoni and S. japonicum cause Katayama fever, hepatic peri-sinusoidal egg granulomas, Symmers' pipe stem periportal fibrosis, portal hypertension, and embolic egg granulomas in the central nervous system. On the other hand, S. haematobium causes hematuria, scarring, calcification, squamous cell carcinoma and egg granulomas in the central nervous system. Only about half of these eggs are eliminated with urine or feces. The rest remain in the body and cause illness and injure vital organs. Signs and symptoms are the body's reaction to the eggs, such as rash and itchy skin, fever, chills, cough and muscle aches within 1-2 months from infection. Other symptoms appear late, depending on the location where they settle and the number of eggs, which manage to penetrate the skin and grow. Some eggs can reach and create trouble in the liver, bladder or the central nervous system. In rare cases, they can cause seizure, paralysis or spinal cord inflammation in the brain or spinal cord. Many cases are asymptomatic (DPHE, DPDx, Kogulan & Lucey).

Signs and Symptoms

The itchy papular rash develops at the site where the cercariae first penetrate the skin (Pearson, 2009). Katayama fever occurs 2-4 weeks after heavy exposure, usually with the start of egg-laying, These symptoms in acute schistosomiasis are more commonly observed and more serious in visitors to specified infested regions than among residents. The symptoms and signs of chronic schistosomiasis are mostly the body's reaction to the eggs retained in the tissues. S. mansoni or S. japonicum can cause mucosal ulcerations, bloody diarrhea, focal fibrosis, strictures, fistulas and papillomatuous growths. Ulcerations in the bladder by S. haematobium may bring on dysuria, hematuria, frequent urination, and chronic cystitis. Secondary bacterial infections in the genitor-urinary tract may also develop. S. mansoni can induce persistent Salmonella septicemia. S. haematorium may cause genital disease or infertility. Their eggs can cause fibrosis and cirrhosis, portal or pulmonary hypertension in the liver or transverse myelitis and seizure in the central nervous system (Pearson).

Diagnosis and Treatment

Schistosomiasis is diagnosed through a urine or stool test for parasites (DHPE, 2010;

DPDx, 2010). The Centers for Disease and Control uses a blood test on a sample taken 6-

8 weeks after exposure. It can be cured with praziquantel taken for 1 or 2 days. If praziquantel is not effective in some areas, oxamniquine is prescribed. Prompt treatment is required to avoid complications. Chronic schistosomiasis is often difficult to cure. By then, damage to the liver, lungs, intestines, or the bladder may be life-long. Complications are, however, rare in those who are only briefly exposed or are not re-infected (DHPE, DPDx).

Epidemiology

Recent statistics reveal that approximately 200 million have been afflicted with schistosomiasis worldwide (DPHE, 2010; DPDx, 2010, Kogulan & Lucey, 2007; Pearson, 2009). Extensive incidence in a given country indicates serious problems with sanitary waste disposal and treatment. The resulting chronic illnesses caused by the disease can significantly impact the socio-economic development of that country. It is prevalent in the regions earlier mentioned and does not respect race. It is more common among males, probably because of their greater exposure to contaminated water through their economic activities. Prevalence is highest among those aged 10-14, although exposure can begin right after birth. Adults are lower risk because of partial immunity or reduced exposure to contaminated water (DPHE, DPDx, Kogulan & Lucey, Pearson).