animal schistosome species in humans, the role of animals as reservoir .. Indications of an inverse relationship between human schisto- somiasis and the. Synopsis of the dynamic processes involved in human and animal schistosomiasis and fascioliasis transmission in the social-ecological system in the study area. human and other hosts and whether this relationship is changing as a result Schistosoma infections of animals in Asia and Latin America.
The zoonotic component of transmission in sub-Saharan Africa appears to be more significant than previously assumed, and may thereby affect the recently revised WHO vision to eliminate schistosomiasis as a public health problem by Moreover, animal schistosomiasis is likely to be a significant cost to affected communities due to its direct and indirect impact on livelihoods.
We argue here for a comprehensive evaluation of the economic burden of livestock and zoonotic schistosomiasis in sub-Saharan Africa in order to determine if extending treatment to include animal hosts in a One Health approach is economically, as well as epidemiologically, desirable.
Animals, Economic evaluation, Humans, One Health, Praziquantel, Schistosomiasis Introduction The One Health approach recognizes that the health of humans is connected to the health of animals and the environment, and aims to encourage collaborative effects of multiple agencies to achieve the best outcomes for each.
However, morphological and subsequent molecular studies of parasites isolated from, for example, children in West Africa have identified viable hybrids of human S.
Current control of human schistosomiasis in Africa is based on preventative chemotherapy PCwhereby populations are mass treated with the donated antihelminthic, praziquantel PZQ.
These programmes, in general, have had impressive effects on reducing human helminthic infection prevalence, intensity and associated morbidity, 8 to the extent that a shift towards interruption of transmission has been argued for in some cases.
Concurrent treatment of zoonotic Schistosoma spp. Therefore, motivating the sustainable involvement of livestock authorities and producers, who may have other disease priorities, can often prove difficult.
Given the potential impact of schistosomiasis on animal health and productivity, a One Health economic evaluation of extending treatment to animal hosts in sub-Saharan Africa appears warranted, and requires data to be gathered on the costs and benefits to both sectors.
With a focus on economic cost aspects, we briefly consider here the available information and highlight current gaps in knowledge. There is also evidence of productivity losses in human populations due to poor school attendance, poorer educational outcomes and reduced worker productivity, such as through lost work days, 1516 as well as costs to tourists of acute schistosomiasis, 17 all of which have not been assessed in current economic evaluations, suggesting that the cost-effectiveness of human treatment may be even higher than currently reported.
Cost-effectiveness of treatment of animal and zoonotic schistosomiasis The economic importance of schistosomiasis to livestock farmers is suspected to be high, although there are substantially fewer data available on the economic impact of schistosomiasis in animals or the cost-effectiveness of their treatment.
Helminth infections of ruminants are widely acknowledged as a constraint on efficient livestock production systems globally 18 and there is some literature available documenting the pathological effects of schistosome infection in animals, such as of S.
There are even fewer data available on the potential costs of treatment, including current spending by farmers on PZQ treatment, where wide-scale treatment programmes would have additional costs, such as the strengthening of veterinary services. There are, furthermore, very few data even on the prevalence and intensity of animal schistosomiasis in sub-Saharan Africa, or on the relative importance of zoonotic transmission cycles to human disease, either in the past nor under current environments under extensive levels of anthropogenic change.
Veterinary use and misuse of antihelminthics increases the risk of drug resistance evolving, particularly since common veterinary schedules for antihelminthic treatment are often more frequent than those used in annual human PC.
Likewise, appropriate veterinary dosages are often not as well studied or always implemented within developing country settings. Furthermore, untreated zoonotic reservoirs may currently be acting as a refugia, slowing the development of drug resistance. Conclusions and recommendations We urgently need reliable estimates of the current prevalence, intensity and pathological burden of animal schistosomes in affected communities in sub-Saharan Africa concurrently incorporating these data within a One Health economic evaluation of extending disease control activities to animal hosts.
Young worms then pair and migrate to their predilection sites in the veins of the gut or bladder. Egg production begins from weeks after infection, and adult worms normally live for years, although some may survive much longer. The eggs are sufficiently characteristic to facilitate specific diagnosis.
- Human schistosomiasis
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On occasion, microscopy of rectal biopsies has been used to diagnose S. Immunoserological tests have been developed to detect host antibodies against infection but they have experienced cross-reactivity problems and cannot discriminate between previous and active infection. More recently, molecular techniques have been used to detect parasite antigens or DNA in host samples; some tests showing good correlations with parasite burdens.
The drug of choice for the treatment of all Schistosoma spp. Nitridazole and metrifonate are effective against S. While timely treatment is effective, cured individuals rapidly become re-infected in endemic areas.
CDC - Schistosomiasis - Biology
Various control programmes have therefore been developed based on mass chemotherapy in conjunction with preventive measures, including improved sanitation, snail vector control, modifying habitats and farming practices, and public education campaigns. Water contamination can be reduced by preventing the ingress of parasite eggs as well as curtailing the asexual amplification cycle in snail hosts.
The provision and use of latrines contains sources of infection, and modern biocomposting toilets appear to be effective in killing parasite eggs when used properly. Snail populations may be reduced by the strategic use of molluscicides niclosamide or copper sulphatedraining marshes and swamps, and clearing channels of vegetation.
Once the cercariae come into contact with a human host they burrow into the skin. The cercariae lose their tails while burrowing into the skin and become schistosomulae.
The adult worms then pair with a mate of the opposite sex and move along blood vessels against the blood flow to the blood vessels near the bowel, rectum or bladder. Once they reach the blood vessels near the bowel, rectum or bladder the worms begin to lay their eggs.
Illustration to show the life cycle of the schistosome parasite. The eggs can lodge in a number of areas around the body causing inflammation swelling. This can then lead to the formation of tissue masses called granulomas and stiffening of the tissue called fibrosis. This can lead to a range of symptoms depending on which organ they are located in. In acute schistosomiasis, symptoms are caused by the immune system reacting to the parasite and are generally short-term and mild. Symptoms of acute schistosomiasis can develop a few weeks after the schistosome parasite first burrows into the skin of its human host.
These symptoms are in response to the first parasite eggs getting trapped in the liver and spleen.
These acute symptoms are generally flu-like, including a high temperature and muscle aches, but can also include a skin rash, cough and abdominal pain. Sometimes acute schistosomiasis symptoms can be so mild they go unnoticed. This means that the schistosomiasis persists for a long time in the body. Chronic schistosomiasis can develop months or even years after the initial infection and cause long-term health problems. Damage to the organs after chronic infection is irreversible.
Pain when urinating — schistosome eggs lodged in the urinary tract cause inflammation and result in symptoms similar to urinary tract and bladder infections.
In rare cases this has been found to predispose individuals to bladder cancer. In females, chronic urinary tract infections are also associated with damage to the cervix, fallopian tubes and vagina.
Blood in the urine — this is the result of a severe bladder inflammation caused by eggs lodged in blood vessels in the wall of the bladder. Bloody diarrhoea — schistosome eggs can lodge in the blood vessels of the intestine causing inflammation, and, consequently, diarrhoea. Chest pain — this is the result of larval parasites moving though the lung tissue and later schistosome eggs becoming trapped in the blood vessels that supply the lungs.
What is schistosomiasis?
These result in inflammation, granuloma formation and fibrosis. Liver failure —the immune response to schistosome eggs lodged in the blood vessels supplying the liver causes the formation of granulomas and scar tissue. Seizures such as a stroke or fit and paralysis — this can be the result of schistosome eggs lodging in the spinal cord or brain, causing inflammation.
Children who are repeatedly infected with schistosomiasis due to constant exposure to contaminated water can develop anaemiamalnutrition and learning disabilities.Unbelievable Friendship! People and Wild Animals - Compilation 2018
The intensity and prevalence of schistosomiasis infection usually rises with age, peaking at around years old.