schistosomiasis

Schistosomiasis

Key Words and Related Terms: leg lymphedema, lymphedema, lymphatic filariasis, loiasis, tungiasis, Elephantiasis, parasites, lymph nodes, Human schistosomiasis, bilharzia, bilharziosis, snail fever

This is another form of lymphedema generally referred to as lymphatic filariasis.

It is caused by an infection (invasive) of the Schistosoma parasite and is endemec in the tropical regions of Asia, Africa and Souther American. It is carried by snails.

Several species can infect humans:

Species of Schistosoma that can infect humans: Schistosoma mansoni (ICD-10 B65.1) and Schistosoma intercalatum (B65.8) cause intestinal schistosomiasis Schistosoma haematobium (B65.0) causes urinary schistosomiasis Schistosoma japonicum (B65.2) and Schistosoma mekongi (B65.8) cause Asian intestinal schistosomiasis Avian schistosomiasis species cause swimmer's itch and clam digger itch

While these infect other animals:

Species of Schistosoma that can infect other animals:

S. bovis — normally infects cattle, sheep and goats in Africa, parts of Southern Europe and the Middle East S. mattheei — normally infects cattle, sheep and goats in Central and Southern Africa S. margrebowiei — normally infects antelope, buffalo and waterbuck in Southern and Central Africa S. curassoni — normally infects domestic ruminants in West Africa S. rodhaini — normally infects rodents and carnivores in parts of Central Africa

Symptoms

These include abdominal pain, cough, diarrhea, eosinophilia - extremely high eosinophil granulocyte count (white blood cell), fever, and fatigue.

Hepatosplenomegaly — the enlargement of both the liver and the spleen. Hepatic schistosomiasis is the second most common cause of esophageal varices[4] worldwide.

Genital sores — lesions that increase vulnerability to HIV infection. Lesions caused by schistosomiasis may continue to be a problem after control of the schistosomiasis infection itself. Early treatment, especially of children, which is relatively inexpensive, prevents formation of the sores.

Skin symptoms: At the start of infection, mild itching and a papular dermatitis of the feet and other parts after swimming in polluted streams containing cercariae.

Though rare, central nervous system lesions can occur. This condition which referred to as Cerebral granulomatous disease may be caused by ectopic S. japonicum eggs in the brain, and granulomatous lesions around ectopic eggs in the spinal cord from S. mansoni and S. haematobium infections may result in a transverse myelitis with flaccid paraplegia.

Schistosomes have a typical trematode vertebrate-invertebrate lifecycle, with humans being the definitive host. When the snails that are in the water where humans might swim, the parasite easily transfers to and burrows into the skin of the human.

They remain in the skin for about 2 days then locating a post-capillary venule. From there, it may travel to the lungs where it undergoes further developmental changes necessary for migration to the liver. This occurs in aproximately 8 days after penetration.

Juvenile S. mansoni and S. japonicum worms develop an oral sucker after arriving at the liver, and it is during this period that the parasite begins to feed on red blood cells. The nearly-mature worms pair, with the longer female worm residing in the gynaecophoric channel of the shorter male. Adult worms are about 10 mm long. Worm pairs of S. mansoni and S. japonicum relocate to the mesenteric or rectal veins. S. haematobium schistosomula ultimately migrate from the liver to the perivesical venous plexus of the bladder, ureters, and kidneys through the hemorrhoidal plexus. Parasites reach maturity in six to eight weeks, at which time they begin to produce eggs. Adult S. mansoni pairs residing in the mesenteric vessels may produce up to 300 eggs per day during their reproductive lives. S. japonicum may produce up to 3000 eggs per day. Many of the eggs pass through the walls of the blood vessels, and through the intestinal wall, to be passed out of the body in feces. S. haematobium eggs pass through the ureteral or bladder wall and into the urine. Only mature eggs are capable of crossing into the digestive tract, possibly through the release of proteolytic enzymes, but also as a function of host immune response, which fosters local tissue ulceration. Up to half the eggs released by the worm pairs become trapped in the mesenteric veins, or will be washed back into the liver, where they will become lodged. Worm pairs can live in the body for an average of four and a half years, but may persist up to 20 years.

Trapped eggs mature normally, secreting antigens that elicit a vigorous immune response. The eggs themselves do not damage the body. Rather it is the cellular infiltration resultant from the immune response that causes the pathology classically associated with schistosomiasis. (1)

The usual incubation period is between 14 - 84 days, however, many people are asymptomatic and have subclinical disease during both acute and chronic stages of infection. Persons with acute infection (also known as Katayama syndrome) may present with rash, fever, headache, myalgia, and respiratory symptoms. Often eosinophilia is present with hepato- and/or splenomegaly. (2)

The most common way of diagnosis involved stool samples, which are microscopically examined and the urin which can also contain eggs. A blood test may also be used as a further confirmation of diagnosis.

Complications from the infections can include:

Bladder cancer

Chronic kidney failure

Chronic liver damage and an enlarged spleen

Colon (large intestine) inflammation with bloody diarrhea

Kidney and bladder obstruction

Pulmonary hypertension

Repeated blood infections can occur, because bacteria can enter the bloodstream through an irritated colon

Right-sided heart failure

Seizures

Treatment is quite effective for the treatment of both urinary and intestinal schisosomiasis. A prescription medication, Praziquantel, is taken for 1 to 2 days to treat the infection.

Treament for the lymphedema should include complete decongestive therapy, meticulous skin care and the wearing of compression garments and bandages.

Most recently artemesinihn derivatives in combination with praziquantel have been shown to be effective against the immature stages of the parasite.

Prevention is also effective. This can include aoivding swimming or even wading in fresh waters in countries where schistosomiasis occurs.

Although schistosomiasis is not transmitted by swallowing contaiminated water, if your mouth or lips come in contact with contaminated water, you could be infected.

Water used for bathing should be brought to a rolling boil for 1 minute to kill any cercariae, and then cooled before bathing to avoid scalding. Water held in a storage tank for at least 1 - 2 days should be safe for bathing.

Vigorous towel drying after an accidental, very brief water exposure may help to prevent the Schistosoma parasite from penetrating the skin. However, do not rely on vigorous towel drying alone to prevent schistosomiasis.

Control efforts in affected countries include reducing the number of infections in human by eliminated the snalis that are required to maintain the parasite's life cycle.

Control measure also can include mass drug treatment of entire communities and targeted treatment of school children. (2)

I would urge anyone traveling to affected areas to find out if the area that they will be traveling is known for the infection. This may be critical in assisting the doctors here in the United States (or other developed countries) in diagnosing the condition.

If treated promptly and effectively the prognosis is generall positive with good results from the treatments.

(1) Wikipedia

(2) CDC

Abstracts and Studies

Schistosomiasis.

Mar 2012

Macconnachie A.

Source

Brownlee Centre, Gartnavel General Hospital, Great Western Road, Glasgow G12 0YN, UK.

alisdair.macconnachie@ggc.scot.nhs.uk.

Abstract

Human schistosomiasis is a common blood fluke infection in the tropics and subtropics. The organism requires a specific fresh water snail intermediate as host and this determines its geographical distribution. Humans become infected following water exposure, with rural communities and children having the highest burden of disease. Travellers to areas of high endemicity are at risk of infection as they frequently engage in pursuits that expose them to fresh water. Disease manifestations range from acute hypersensitivity reactions to chronic illness with intestinal, hepatic and bladder disease. Infection can often be asymptomatic and travellers to endemic areas should be screened for schistosomiasis after return. Treatment is highly effective, even in advanced disease, and the diagnosis should be considered in individuals with possible clinical illness who have travelled to or lived in endemic areas.

PubMed

Reductions in genetic diversity of Schistosoma mansoni populations under chemotherapeutic pressure: The effect of sampling approach and parasite population definition.

Mar 2012

French MD, Churcher TS, Basáñez MG, Norton AJ, Lwambo NJ, Webster JP.

Source

Schistosomiasis Control Initiative, Imperial College London, Faculty of Medicine, Norfolk Place, London W2 1PG, UK; Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK.

Abstract

Detecting potential changes in genetic diversity in schistosome populations following chemotherapy with praziquantel (PZQ) is crucial if we are to fully understand the impact of such chemotherapy with respect to the potential emergence of resistance and/or other evolutionary outcomes of interventions. Doing so by implementing effective, and cost-efficient sampling protocols will help to optimise time and financial resources, particularly relevant to a disease such as schistosomiasis currently reliant on a single available drug. Here we explore the effect on measures of parasite genetic diversity of applying various field sampling approaches, both in terms of the number of (human) hosts sampled and the number of transmission stages (miracidia) sampled per host for a Schistosoma mansoni population in Tanzania pre- and post-treatment with PZQ. In addition, we explore population structuring within and between hosts by comparing the estimates of genetic diversity obtained assuming a 'component population' approach with those using an 'infrapopulation' approach. We found that increasing the number of hosts sampled, rather than the number of miracidia per host, gives more robust estimates of genetic diversity. We also found statistically significant population structuring (using Wright's F-statistics) and significant differences in the measures of genetic diversity depending on the parasite population definition. The relative advantages, disadvantages and, hence, subsequent reliability of these metrics for parasites with complex life-cycles are discussed, both for the specific epidemiological and ecological scenario under study here and for their future application to other areas and schistosome species.

SciVerse

Diagnosis of imported schistosomiasis: Evaluation of eight serological tests.

Mar 2012

Kinkel HF, Dittrich S, Bäumer B, Weitzel T.

Source

Institute of Tropical Medicine and International Health, Charité - University Medicine Berlin, Berlin, Germany.

Abstract

The diagnosis of schistosomiasis in individuals from non-endemic countries is challenging and few data are available on the accuracy of serological diagnosis in those patients. We evaluated the performance of eight serological assays, including four commercial kits, in the diagnosis of imported schistosomiasis in individuals from non-endemic areas: six enzyme-linked immunosorbent assays using three different antigens, an indirect hemagglutination assay, and an indirect immunofluorescence antibody test. To analyze the assays, we used a total of 141 serum samples, 121 derived from patients with various parasitic infections, among those 37 cases of schistosomiasis, and 20 from healthy volunteers. The sensitivity values to detect schistosomiasis cases ranged from 41% to 78% and were higher in Schistosoma mansoni than in S. haematobium infections. Specificity values varied from 76% to 100%; false positive results were most frequent in samples from patients with cestode infections. By combining two or more tests, sensitivity improved markedly and specificity only moderately decreased.Serological tests are a useful instrument to diagnose imported schistosomiasis in non-endemic countries, but due to limitations in test sensitivities, we recommend the use of two or more assays in parallel.

Clinical and Vaccine Immunology

Testicular schistosomiasis: A case report.

Mar 2012

Badmus TA, Takure AO, Osasan SA, Olajide AO, Sabageh DO.

Source

Department of Surgery, College of Health Sciences, Obafemi Awolowo University.

Abstract

AIMS AND OBJECTIVES: To report a case of testicular Schistosomiasis with a suspicion of testicular cancer.

PATIENT AND METHODS: Hospital record of a 16 year old patient with histopathology confirmation of testicular Schistosomiasis was reviewed and summarised. The patient who had painless testicular nodules and ultrasound features of heterogenous echotexture and hypoechoic focus was diagnosed as testicular cancer and treated with radical orchidectomy. Histopathology confirmed testicular Schistosomiasis and the patient had additional praziquantel therapy.

RESULTS: Patient was followed up for over 26months post-operative.

CONCLUSIONS: Testicular Schistosomiasis can mimick malignant testicular tumour. Hard nodular testicular mass in a patient with recent past history of schistosomiasis should arouse suspicion of testicular Schistosomiasis. Awareness and early presentation will prevent unwarranted orchidectomy.

PubMed