Schistosomiasis Amgad.2008journalwnsz (recovered)

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Contents Introduction ........................................................................................................................... .....3 Geographical Distribution of occurrence.....................................................................................6

Pathogenesis...................................................................................................... ..........................8 The disease of man.................................................................................................................... ..9 The disease of animal................................................................................................................ ..10 Source of infection & Mode of Transmission ............................................................................11

Role of animal in the epidemiology of the disease..................................................................... 12 Diagnosis............................................................................................................ .........................13

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Schistosomiasis Synonym:Bilharziasis, katayama syndromes (a cute schistosomiasis)

Aetiology: The primary gents of human schistosomiasis are the three classic species of blood trematodes: Schistosoma mansoni. Schistosoma japonicum. Schistosoma haematobium. Occasionally, man is invaded by species of Schistosoma that parasitize other animals. Because of their close relationship to the classic species, non human schistosomes have been grouped with them into complexes. S. Rodhaini, a parasite of dogs, cats and rodents belongs to the mansoni complex. S. Margrebowiei, a parasite of antelopes, bovine, equines &sheep belongs to the japonicum complex. This also includes S.Mekongi species. Species that infects man and dogs in Kampuchea(Voge etal,1974)assigned to the Haematobium complex are;A-S.bovis (bovines, camels, goats, sheep &pigs) B-S.mattheei (bovines, goats, sheep rodents, &other animals) C-S.intercalatum (domestic &wild ruminants of central Africa) *-Mixed infections between human &animal species occur with some frequency in parts of the old world. The different strains of Schistosoma vary in their infectivity for snails and snail species, as well as populations within the species, and vary in their susceptibility to the parasite,

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Schistosomes live in the vascular system. S.Mansoni is found primarily in the mesenteric veins that drain the large intestine and especially in the sigmoid branches and S.Hematobium locates in the plexuses of the vena cava system that drains the bladder, pelvis and uterus. The eggs are shed mainly with the faecal matter in infections caused by S.Mansoni and with the urine in the parasitosis caused by S.Hematobium. The eggs hatch when they reach fresh water and the released miracidia larvae ref {E.J.L.Soulsby}. Miracidia infect aquatic snails which are the intermediated host, S.Mattheei infects bulinus (Physopsis) africanus, B. (p.)Globosus and B. (P.) nastusus. Schistosomes bovis also infects these snails and in additions, bulinus truncates has been implicated as an intermediate host ref {Malek, 1961}. While intermediate host of S.Mansoni are planorbids of genus biomphalaria, especially biomphalaria glabrata. Schistosoma hematobium develops in bulinus truncatus, B.forskali and B. Obtusispira, and S.Spindale develops in snails of the genera planorbis, indoplanorbis and lymnaea The Miracidia which invade suitable water snails &develop through Primary & Secondary sporocysts to become cercaria, when fully Mature The cercaria leave the snail & swim freely in the water, Ultimately gives rise to cercaria with a frocked tail. Approximately 1 month elapses from Penetration of the Miracidium of Schistosoma Mansoni into a suitable snail to the emergence of cercaria.

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A single Miracidium can give rise to more than 100.000 cercar

Figure 1

Emergence of cercaria from the snail is periodic of those of S.mansoni tend to emerge in daylight 09.00 to 14.00 hours. Although emergence is inhibited or partially inhabited to temperature of below 21C◦ peak shedding of cercaria of S.matteei occurs at about 17c◦ and in the eastern Transvaal this occurs between 21:00 – 14:00 hours in mid-water and 06:00 – 08:00 hours in summer. Infection of the definitive host is though active skin penetration of the cercaria although cercaria may penetrate the wall of the rumen when swallowed with water. Skin penetration is assisted by the secretions of the cephalic glands which digest the tissues. The cercaria transform into Schistosomula

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which are transported to the lungs via the circulation within seven days. They are then carried to the river, presumably via the blood stream, and from eight days on words schistosomula are found in the portal vessels of the liver. Pairing of the worms takes place in the portal veins before they leave the liver to reach Maturity in the Mesenteric veins. 4- Schisms Cattle and Horses may become infected when standing in the shallow waters of dams, rivers, etc. During the heat of day, they and other animals are also infected orally when water tanks of other source of drinking water become infected with snails and contaminated with fecal material. Geographical Distribution of occurrence:Shistosomiasis occur in 79 developing countries that together have a population of the three billion inhabitants, approximately 600 million of when are at risk of contracting the disease (Mahmoud, 1984). S. mansoni has the widest geographical distribution; it is found in 52 countries located in Arica, the eastern Mediterranean, the Caribbean, and South American. Schistosoma bovis: (sonsino, 1876) occurs in portal and mesenteric veins of cattle, sheep and goats in central, east and West Africa, the Mediterranean area and in the middle east.ref {E.J.L.soursby}. Schistosoma mansoni: sambon, 1907 occurs in the mesenteric veins of man in Africa, South America and the Middle East and humans are the most important definitive host. However, a variety of animals have been found to be naturally infected with Schistosoma mansoni these include gerbils and Nile rats in Egypt, rodents in southern Africa and Zaire, various species of rodents and wild mammals and cattle in Brazil and baboons, rodents and dogs in east Africa .up to 50% of baboons are infected in some areas in east Africa. The Nile Delta is a hyper endemic area of Schistosoma mansoni infection. Autochthonous cases also occur in Yemen and Saudi Arabia. Schistosoma haematobium: the agent of vesicle schistosomiasis is endemic in 53 countries in Africa, as well as in the Middle East and a locus of infection has been reported in India. Man is the only significant maintenance host of this species although the infection has been found in animal, e.g. baboons and monkeys in east Africa, rodents in Kenya and eastern Africa ,pigs in Nigeria and chimpanzees in west Africa . There is no unequivocal evidence that animals play a role in the human disease. According to various estimates, 100 to 300 million people in the world are infected by one or another species of Schistosoma.

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In Africa, the construction of dams has also contributed greatly to the infections spread. In different areas of that continent, rates of infection by S. Mansoni and S. Haematobium vary from 10 to 80%. It is estimated there are close to a million infected persons in Yemen. Map 1.1 schistosomiasis .Geographic distribution of Schistosoma haematobium appear in Sudan and Other countries of Africa

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Map 1.2 schistosomiasis .Geographic distribution of Schistosoma mansoni appear in Sudan .

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Pathogenesis:Injury to the definitive host can result from the presence of adults in the veins, ova in veins or tissues or cercaria as they penetrate the skin. The adult blood flukes living within the veins may produce some phlebitis with Intiman proliferation and occasionally venous thrombosis. Vascular lesion are most likely to be severe when the adult worms die or are trapped in UN usual sites. The adult schistosomes also consume erythrocytes and discharge blood pigment, which is engulfed by macrophages and may be found in reticuloendothelial tissues in the liver and spleen this pigment appears in the cytoplasm of macrophages as black granules, the ova of the blood flukes are the most important factors in the production of lesion. The ova deposited in the venules reach venous capillaries adhere to and become embedded within the endothelium rupture the basement membrane by means of enzymes secreted through the pores of the egg shell by the miracidium within, and escape into the tissues to make their way to the lumen of the intestine or urinary bladder. This migration lead to small hemorrhagic ulcers, which in extensive infestations to antigens released by the eggs. This hypersensitivity reaction lead to the formation of granulomas composed of neutrophils, lymphocytes, macrophages and multinucleated giant cells.

These granulomas or pseudotubercals are a characteristic feature of schistosomiasis and may be wide spread, leading to extensive tissue damage. The tissue reaction and microscopic appearance of the egg shell are characteristic. The ziehl- nelson stain is useful in differentiating some Schistosoma eggs.

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Cutaneous lesions develop in humans and animals as Aversa of penetration of the skin by cercaria of Schistosomes the intensity of the tissue reaction depends to some extent upon the sensitivity and resistance of the host to the parasite. As the cercaria reach the dermis, a leukocytic reaction of varying intensity results, including neutrophils, lymphocyte & eosinophile this is accompanied by urticaria, itching & the formation of ting nodules that elevate the epidermis. In sensitised animals or humans, a sever tissue reaction occurs, and death of the parasite in dermis may set up a prolonged local tissue reaction. Cercaria have the ability to penetrate the epidemics of hosts in which complete development of the fluke does not occur; in this case the cercaria die in the dermis, this is the basis of cercaria dermatitis (swimmer’s itch, collector’s itch, swamp itch).

The Disease in Man:The majority of infected persons harbour few parasite; it is estimated that less than 10% of those infected have along number of parasites and suffer a severe chronic disease of the liver or the urinary tract. School- age children and occupational groups such as fishermen, who enter the water frequently and stay a long time, have more intense infections due to the accumulation of parasites .ref{ Warren,1982}. The symptomatology of schistosomiasis as it develops is generally divided into four phases. The first phase:Corresponds to penetration by the cercaria and is sometimes manifested by dermatitis. The second phase:Corresponds to invasion by the schistosomula; this stage may pass a symptomatically or may be evidenced by coughing and a sthmati form crises caused by the passage of the parasite through the pulmonary capillaries.

The third phase:-

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The acute or toxaemic stage corresponds to the maturation of the parasite and the beginning of ovipositor; it is characterized by. Fever. Prostration. Anorexia. Diarrhoea. Eosinophillia. At times discrete hepatosplenomegally. The fourth phase( chronic phase):Corresponds to proliferation of the parasite and tissular inflammation caused by egg deposition in different organ, S.Mansoni in man primarily gives rise to lesion in the intestinal wall; in time the spread to the liver and produce interlobular fibrosis and portal hypertension, ascites and splenomegaly. In advanced stage there may be pulmonary lesions and respiration symptoms. In the chronic phase, the intestinal, hepato intestinal, hepato splenic and pulmonary clinical form can be distinguished. S.hematobium in man the lesion and symptoms mainly involve the urogenital tract and to a lesser extent the intestine. Papillomatous fold, pseudo abscesses and military pseudo tubercles form in the wall of the bladder; obstruction of the urethra and the ureters is common. The main symptoms of S.Haematobium consist of hematuris , painful and frequent urination. The species of non human schistosomes ,such as S.Bovis, S.Rodhaini and S.Margrebowiei, produce an abortive infection in man . N.B; { the parasite does not reach maturity}.

Disease in animals:The migration of large numbers of schistosomula through the lungs may cause a temporaray cough but this is rare. Acute heavy infections are manifested by profuse diarrhea or dysentery, dehydration and anorexia, these signs develop at the time of patency seven to nine weeks after infections. Anaemia and hypoalbuminaemia are present, sometimes with oedema. There is marked decrease in production or loss of weight. Chronically infected animals are emaciated, microscopically eosinophilia, anaemia, hypoalbuminaemia and perhaps hypergammaaglobulinaemia. Neurological signs may be seen.

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Experimental infection of six calves with 30,000 cercaria of S.Mansoni lesions similar to those occurring in man and other vertebrates were observed in autopsy. The eggs were viable and produced miracidia that were infective for Biomphalaria Globrata .the rate of natural S.Mansoni infection in bovines in an endemic area of minas gerais .Brazil, was low (less than 3%) ref{Coelho et al., 1982}. At presence time In White Nile State, Sudan , there were approximately 813 samples of feaces from different species of animal during 2008,which render the rate of infection jumping to 26% this apparently in the pie chart diagram with comparing to common disease in the same year .

Percentage of diseases during 2008

Source of infection & Mode of Transmission :Schistosomiasis is very important in Pupluc Heahth because of the debilitating effect it has on people throughout large areas of the world . The opening of new agricultural areas by irrigation projects creates an environment favorable for snail reproduction . And the migration of parasitized individuals provides a source of infection for the Mollusks . An example of the influence of environmental changes on the disease is the construction of the aswan dam in Egypt . This dam , which has benefited the national economy , has also wrought profound ecologic change in the region and has favored the increase of population of Mollusks that serve as the intermediate hosts of S. mansoni , but not of S. haematobium . Before construction of the dam , s. mansoni schistosoiasis was common in the Nile Delta , but not very frequent in the region from Cairo to Khartoum (Sudan). These changes faroverd both Penetration of mirasidia into snails and human contact with the cercaria that emerge from them .Furthermore , an increase occurred in human activity connected with the Nile , such as fishing and washing of clothes and utensils.The growing frequency of large dam construction in developing countries , some times without the ecologic and epidemiologic studies needed to established preventive measures , bring s with it the spread and intensification of schistosmaisis . Snails of the genera Biomphalaria & Bulinus , intermediate host for S.mansoni & S.haemtobium , respectively , one aquatic Mollusks that flourish in irrigation canals , lagoons , river back waters & small Nalural poolsof water

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Hybridization between S.haematobium and ( animal ) schistosomes has important repercussions on control . Beside introducing the possibility of an animal reservoir , the hybridization Provoks worry because the hybrids of S.haematobium & S. mattheei show graeter infectivity for snail , mature more quickly ,and produce more eggs ( Wright and Ross,1980). Studies carried out in endemic areas have confirmed that the infectivity of most bodies of water is low ; less than 5% of snails are infected , and cercaria are dispersed throughout a large volume of water .Often with concentration as low as one (1)per liter of water . Like wise ,cercariado not survive more than afew hours if they do not find a suitable definitive host . These facts indicates that when contact with contaminated water is brief,the resulting human infection will usually be mild and asymptomatic (Warren,1982). The infection depends on the population or individuals length of exposure to water contaminated with cercaria . The most regions schistosomiasis is primarily a disease of (1) farm lsborers who work in irrigated fields (rice ,sugarcane) (2) and fishermen who work in fish culture ponds & River .(3) Another exposed group is women who wash clothes or utensils along the banks of pools or streams .(4) the infction can also be contracted while bathing , swimming , and playing in water . Avery interesting aspect of infection by schistosomes is cross or heterologous immunity , for which the unsuitable name (Zooprophylaxis )has been proposed. In many areas of Africa , Manis exposed to cercaria of animal schistosomes which are often more abundant than those of S.heamatobium and S.mansoni and originate in the same Mollusks. Experimental evidence show that the infections caused by heterologous species confer partial immunity , consisting of attenuation of the sererity of the natural disease and resistance against reinfection. Such protection can occur both in man infected with animal strains and in animals infected with human species (S.Mansoni or S.Hematobuim). Role of animals in the epidemiology of the disease:-

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Man is the main reservoir of S.Hematobium and S. Mansoni, this disease can be considered as common to man and animals; the parasitecan move freely between species through the intermediate hosts, except in a few situation of physiologic adaptation (geographic strain).

Diagram of diseases in WNS in Sudan,2008 1

The role of animals in schistosomiasis caused by S. Mansoni is more difficult to define the animals may contribute to the spread and prevalence of the parasitosis. Observations made in Africa indicate that baboons (papio spp) can maintain the parasitosis in their population and can give rise to human infections. N.B; / man is an accidental host in infections caused by animal schistosomes, but evidence indicates that some species (S. Intercalatum and S. Mattheei) have atendency to adapt to humans. Epidemiology studies of S.bovis of infection of cattle in the Sudan showed a significant fall in age-specific prevalence and intensity, based on faecal egg counts (Majid et al. 1980) and this was demonstrated to be due to naturally acquired resistance of S.Bovis (Bushara et al, 1980). Diagnosis:Specific diagnosis is based on demonstrating the presence of egg in fecal material or in both urine and feces (for S.Hematobium ). Non operculate eggs are characteristic of each species of human schistosome. Egg of S.Mansoni are yellowish brown, measure 110 to 180 microns in length by 40 to 70 microns in width, and have a characteristic lateral spine. The eggs of S. Haematobium are approximately the same size and have a very pronounced terminal spine.in advanced chronic cases, eggs may be few and difficult to find; thus , if the faecal examination is negative, Kato’s thick film method, concentration by formalin-ether or acid-ether, or examination of rectal scrapings (S.Mansoni) should be tried. The presence of the parasite’s eggs is undeniable proof of infection, and examination of faeces or urine should always be part of the diagnosis procedure. Proctoscopy may reveal small ulcerations and nodules. 16

The various immunobiologic tests ; 1) complement fixation, 2)precipitation,3) circumoval radial immune precipitation, 4) flocculation, 5) hemagglutination, 6) immunofluorescence, 7) thin layer immunoassay all of these are useful, but they lack specificity and some lack sensitivity. The recently introduced ELISA test has the advantage of allowing deterimination of hte different types of antibodies (IgM, IgE, IgG) produced during the course of the infection, as well as the proportion of antibodies against different parasitic antigens (Egg, Cercaria and adult) in the acute and chronic disease ( Lunde and Ottosen, 1980). Although may serologic methods are currently available, their limited specificity has restricted their wider use in diagnosis and epidemiologic studies (world health organization, 1980).

Treatment:The recent development of praziquantel seems to provide the drug of choice for the treatment of schistosomiasis in man. Generally the therapy of animal schistosomiasis has followed that for the treatmentof human infections, but great care must be taken since very variable results have been obtained. Many of the drugs kill the adult schistosomes en masse and theses then become emboli in the portal veins; portal occlusion and hepatic infarction may result and hepatic failure may occur. The treatment of cattle infected with S.mattheei has been discussed by Lawrence (1978a). Tartar emetic, antimosan and stibophen have been effective in the treatment of S.mattheei in cattle but their use has been associated with deaths among the treated animals. However, stibophen, the sodium salt of antimosan, was very effective in cattle at a dose rate of 7.5 mg/kg given daily for six days. Lucanthone is also effective in the treatment of S.mattheei in both cattle and sheep; 30mg/kg given on three alternate days was effective in cattle and moderate efficacy. Was seen when sheep received 30-50 mg/kg for three days. Hycanthone has been used to treat sheep and an intramuscular injection of 3 mg/kg was moderately effective while 6mg/kg was highly effective. In addition, niridazole was effective insheep at a dose rate of 100mg/kg for three days. Very variable results have been obtained when trichlorophon has been used to treat infected cattle and sheep. Thus, trichlorophon was effective against S.bovis in cattle when 50-70mg/kg was given orally on four to six occasions at three-days intervals. However, 75mg/kg was highly toxic in some treated cattle infected with S. Mattheei. The lack of preparatory starvation of the animls in the latter experiment may have affected the toxicity.

Control:Control of schistosomiasis is based on control of the snail intermediate host and treatment of infected persons and animals. 17

Biological control has proved effective experimentally but has not yet been shown to be effective in the field. The larval stages of Echinostoma spp. Are predatory on schistosome larvae within the snail intermediate host. However, the definitive host of echinostomes are limited in their distribution which makes their use in nature impractical. Microsporidial protozoa such as Nosema eurytremae can cause extensive damage to the intramolluscan stages of schistosomes and other trematodes. Snail population can be limited to low levels by the periodic application of molluscicides such as Frescon and bayluscide to bodies of water. Also contract between man and animals and snail-infested water should be prevented. The fencing off of lakes and pools and the provision of piped drinking water to troughs aid in preventing infection in animals. In addition, water troughs should be mechanically cleaned periodically. The molluscan intermediate hosts of schistosomes prefer slow-moving or stationary water, so that an increase in the speed of water in irrigation channels will reduce the snail populations. The education of humans at risk, the provision of sanitary facilities and the provision of piped water to houses, laundry units and swimming pools reduces human contact with contaminated water.before night soil is allowd to contaminated water it should be treated by fermentation for 25-45 days. The heat created is sufficient to kill schistosome eggs. When contact with water cannot be prevented, since farmers and other workers may have to enter water as part of their livelihood, these workers should be provided with protective clothing. Also, repellants such as dibutylphthalate and benzyl benzoate applied to exposed skin may be effective in preventing penetration by schistosome miracidia.

Reference: 1- E. J. L. Soulsby (1982) Trematoda Rudolphi .Helminths, Arthropods and protozoa of Domesticated animals ., 72-80. 2- Pedro N. Acho and Boris Szyfres ,schistosomiasis, zoonosis and communicable diseases common to man and animal,689-703pp. 1994. 3- Merk veterinary manual, ninth edition ,28-30pp.,1998. 4- Rabak veterinary research laboratory record .2008.

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