Schistosomiasis Amgad.2008journalWNSZ (Recovered)

8/14/2019 Schistosomiasis Amgad.2008journalWNSZ (Recovered)

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ContentsIntroduction...........................................................................................................................

.....3Geographical 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 thedisease..................................................................... 12

Diagnosis.....................................................................................................................................13

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SchistosomiasisSynonym:-

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 parasitizeother animals. Because of their close relationship to the classic

species, non human schistosomes have been grouped with them intocomplexes.S. Rodhaini, a parasite of dogs, cats and rodents belongs to themansoni complex.S. Margrebowiei, a parasite of antelopes, bovine, equines &sheepbelongs to the japonicum complex. This also includes S.Mekongispecies.Species that infects man and dogs in Kampuchea(Vogeetal,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 somefrequency in parts of the old world.

The different strains of Schistosoma vary in their infectivity for snailsand snail species, as well as populations within the species, and vary intheir susceptibility to the parasite,

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Schistosomes live in the vascular system. S.Mansoni is found primarilyin the mesenteric veins that drain the large intestine and especially inthe sigmoid branches and S.Hematobium locates in the plexuses of thevena cava system that drains the bladder, pelvis and uterus.

The eggs are shed mainly with the faecal matter in infections causedby S.Mansoni and with the urine in the parasitosis caused by

S.Hematobium. The eggs hatch when they reach fresh water and the releasedmiracidia 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, bulinustruncates has been implicated as an intermediate host ref {Malek,1961}. While intermediate host of S.Mansoni are planorbids of genusbiomphalaria, especially biomphalaria glabrata. Schistosomahematobium 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 throughPrimary & Secondary sporocysts to become cercaria, when fully Mature

The cercaria leave the snail & swim freely in the water, Ultimatelygives 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.mansonitend to emerge in daylight 09.00 to 14.00 hours. Although emergenceis inhibited or partially inhabited to temperature of below 21C peakshedding of cercaria of S.matteei occurs at about 17c and in the easternTransvaal 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 thecercaria although cercaria may penetrate the wall of the rumen whenswallowed with water.Skin penetration is assisted by the secretions of the cephalic glandswhich digest the tissues. The cercaria transform into Schistosomula

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which are transported to the lungs via the circulation within sevendays.

They are then carried to the river, presumably via the blood stream,and from eight days on words schistosomula are found in the portalvessels 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- SchismsCattle and Horses may become infected when standing in the shallowwaters of dams, rivers, etc. During the heat of day, they and otheranimals are also infected orally when water tanks of other source of drinking water become infected with snails and contaminated withfecal material.Geographical Distribution of occurrence:-Shistosomiasis occur in 79 developing countries that together have apopulation 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 isfound in 52 countries located in Arica, the eastern Mediterranean, theCaribbean, and South American.

Schistosoma bovis: (sonsino, 1876) occurs in portal andmesenteric veins of cattle, sheep and goats in central, east and WestAfrica, the Mediterranean area and in the middle east.ref {E.J.L.soursby}.

Schistosoma mansoni: sambon, 1907 occurs in themesenteric veins of man in Africa, South America and the Middle Eastand humans are the most important definitive host. However, a variety

of animals have been found to be naturally infected with Schistosomamansoni these include gerbils and Nile rats in Egypt, rodents insouthern Africa and Zaire, various species of rodents and wildmammals and cattle in Brazil and baboons, rodents and dogs in eastAfrica .up to 50% of baboons are infected in some areas in east Africa.

The Nile Delta is a hyper endemic area of Schistosoma mansoniinfection. Autochthonous cases also occur in Yemen and Saudi Arabia.

Schistosoma haematobium: the agent of vesicleschistosomiasis is endemic in 53 countries in Africa, as well as in theMiddle East and a locus of infection has been reported in India. Man is

the only significant maintenance host of this species although theinfection has been found in animal, e.g. baboons and monkeys in eastAfrica, rodents in Kenya and eastern Africa ,pigs in Nigeria andchimpanzees in west Africa . There is no unequivocal evidence thatanimals play a role in the human disease.According to various estimates, 100 to 300 million people in the worldare infected by one or another species of Schistosoma.

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In Africa, the construction of dams has also contributed greatly to theinfections spread. In different areas of that continent, rates of infectionby S. Mansoni and S. Haematobium vary from 10 to 80%. It isestimated there are close to a million infected persons in Yemen.

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Map 1.1 schistosomiasis .Geographic distribution of Schistosomahaematobium 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 adultsin 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 phlebitiswith Intiman proliferation and occasionally venous thrombosis. Vascular lesionare most likely to be severe when the adult worms die or are trapped in UNusual sites.

The adult schistosomes also consume erythrocytes and discharge bloodpigment, which is engulfed by macrophages and may be found in

reticuloendothelial tissues in the liver and spleen this pigment appears in thecytoplasm of macrophages as black granules, the ova of the blood flukes arethe most important factors in the production of lesion.

The ova deposited in the venules reach venous capillaries adhere to andbecome embedded within the endothelium rupture the basement membraneby means of enzymes secreted through the pores of the egg shell by themiracidium within, and escape into the tissues to make their way to thelumen of the intestine or urinary bladder.

This migration lead to small hemorrhagic ulcers, which in extensiveinfestations to antigens released by the eggs. This hypersensitivity reactionlead 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 tissuedamage. The tissue reaction and microscopic appearance of the egg shell arecharacteristic. The ziehl- nelson stain is useful in differentiating someSchistosoma eggs.

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Cutaneous lesions develop in humans and animals as Aversa of penetrationof the skin by cercaria of Schistosomes the intensity of the tissue reactiondepends to some extent upon the sensitivity and resistance of the host to theparasite.

As the cercaria reach the dermis, a leukocytic reaction of varyingintensity results, including neutrophils, lymphocyte & eosinophile this isaccompanied by urticaria, itching & the formation of ting nodules that elevatethe epidermis. In sensitised animals or humans, a sever tissue reactionoccurs, and death of the parasite in dermis may set up a prolonged localtissue reaction.

Cercaria have the ability to penetrate the epidemics of hosts in whichcomplete development of the fluke does not occur; in this case the cercariadie in the dermis, this is the basis of cercaria dermatitis (swimmers itch,collectors itch, swamp itch).

The Disease in Man:-

The majority of infected persons harbour few parasite; it is estimated thatless than 10% of those infected have along number of parasites and suffer asevere chronic disease of the liver or the urinary tract.

School- age children and occupational groups such as fishermen, who enterthe water frequently and stay a long time, have more intense infections dueto the accumulation of parasites .ref{ Warren,1982}.

The symptomatology of schistosomiasis as it develops is generally dividedinto four phases.

The first phase:-

Corresponds to penetration by the cercaria and is sometimes manifested bydermatitis.

The second phase:-

Corresponds to invasion by the schistosomula; this stage may pass asymptomatically or may be evidenced by coughing and a sthmati form crisescaused 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 parasiteand 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 causedby egg deposition in different organ, S.Mansoni in man primarily gives riseto lesion in the intestinal wall; in time the spread to the liver and produceinterlobular fibrosis and portal hypertension, ascites and splenomegaly.

In advanced stage there may be pulmonary lesions and respirationsymptoms. In the chronic phase, the intestinal, hepato intestinal, hepatosplenic and pulmonary clinical form can be distinguished.

S.hematobium in man the lesion and symptoms mainly involve theurogenital tract and to a lesser extent the intestine.

Papillomatous fold, pseudo abscesses and military pseudo tubercles form inthe wall of the bladder; obstruction of the urethra and the ureters is common.

The main symptoms of S.Haematobium consist of hematuris , painful andfrequent urination.

The species of non human schistosomes ,such as S.Bovis, S.Rodhaini andS.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 maycause a temporaray cough but this is rare. Acute heavy infections aremanifested 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 withoedema.

There is marked decrease in production or loss of weight. Chronically infectedanimals are emaciated, microscopically eosinophilia, anaemia,hypoalbuminaemia and perhaps hypergammaaglobulinaemia. Neurologicalsigns may be seen.

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Experimental infection of six calves with 30,000 cercaria of S.Mansoni lesionssimilar to those occurring in man and other vertebrates were observed inautopsy.

The eggs were viable and produced miracidia that were infective forBiomphalaria Globrata .the rate of natural S.Mansoni infection in bovines inan endemic area of minas gerais .Brazil, was low (less than 3%) ref{Coelho etal., 1982}.

At presence time In White Nile State, Sudan , there were approximately 813samples of feaces from different species of animal during 2008,which renderthe rate of infection jumping to 26% this apparently in the pie chart diagramwith 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 thedebilitating effect it has on people throughout large areas of the world .

The opening of new agricultural areas by irrigation projects creates anenvironment 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 theconstruction of the aswan dam in Egypt . This dam , which has benefited thenational economy , has also wrought profound ecologic change in the regionand has favored the increase of population of Mollusks that serve as theintermediate hosts of S. mansoni , but not of S. haematobium .

Before construction of the dam , s. mansoni schistosoiasis was common inthe Nile Delta , but not very frequent in the region from Cairo to Khartoum(Sudan).

These changes faroverd both Penetration of mirasidia into snails and humancontact with the cercaria that emerge from them .Furthermore , an increaseoccurred in human activity connected with the Nile , such as fishing andwashing of clothes and utensils.The growing frequency of large damconstruction in developing countries , some times without the ecologic and

epidemiologic studies needed to established preventive measures , bring swith 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 inirrigation canals , lagoons , river back waters & small Nalural poolsof water

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Hybridization between S.haematobium and ( animal ) schistosomes hasimportant repercussions on control . Beside introducing the possibility of ananimal reservoir , the hybridization Provoks worry because the hybrids of S.haematobium & S. mattheei show graeter infectivity for snail , mature morequickly ,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 cercariaare dispersed throughout a large volume of water .Often with concentrationas low as one (1)per liter of water . Like wise ,cercariado not survive morethan afew hours if they do not find a suitable definitive host .

These facts indicates that when contact with contaminated water is brief,theresulting human infection will usually be mild and asymptomatic(Warren,1982).

The infection depends on the population or individuals length of exposure towater contaminated with cercaria .

The most regions schistosomiasis is primarily a disease of (1) farm lsborerswho work in irrigated fields (rice ,sugarcane) (2) and fishermen who work infish culture ponds & River .(3) Another exposed group is women who washclothes or utensils along the banks of pools or streams .(4) the infction canalso be contracted while bathing , swimming , and playing in water .

Avery interesting aspect of infection by schistosomes is cross or heterologousimmunity , for which the unsuitable name (Zooprophylaxis )has beenproposed.

In many areas of Africa , Manis exposed to cercaria of animal schistosomeswhich are often more abundant than those of S.heamatobium and S.mansoniand originate in the same Mollusks.

Experimental evidence show that the infections caused by heterologousspecies 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 inanimals 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.Hematobiumand S. Mansoni, this disease can be consideredas common to man and animals; theparasitecan move freely between speciesthrough the intermediate hosts, except in afew situation of physiologic adaptation

(geographic strain). The role of animals in schistosomiasis causedby S. Mansoni is more difficult to define theanimals may contribute to the spread andprevalence of the parasitosis.

Observations made in Africa indicate thatbaboons (papio spp) can maintain theparasitosis in their population and can giverise to human infections.

N.B; / man is an accidental host in infectionscaused by animal schistosomes, but evidenceindicates that some species (S. Intercalatumand S. Mattheei) have atendency to adapt tohumans.

Epidemiology studies of S.bovis of infectionof cattle in the Sudan showed a significant fallin age-specific prevalence and intensity,based on faecal egg counts (Majid et al.1980) and this was demonstrated to be dueto naturally acquired resistance of S.Bovis(Bushara et al, 1980).

Diagnosis:-

Specific diagnosis is based on demonstrating the presence of egg in fecalmaterial or in both urine and feces (for S.Hematobium ). Non operculate eggsare characteristic of each species of human schistosome. Egg of S.Mansoniare yellowish brown, measure 110 to 180 microns in length by 40 to 70microns 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 tofind; thus , if the faecal examination is negative, Katos thick film method,concentration by formalin-ether or acid-ether, or examination of rectalscrapings (S.Mansoni) should be tried. The presence of the parasites eggs isundeniable proof of infection, and examination of faeces or urine shouldalways be part of the diagnosis procedure. Proctoscopy may reveal smallulcerations and nodules.

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Diagram of diseases in WNS inSudan,2008 1


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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 allowingdeterimination of hte different types of antibodies (IgM, IgE, IgG) producedduring the course of the infection, as well as the proportion of antibodiesagainst different parasitic antigens (Egg, Cercaria and adult) in the acute andchronic disease ( Lunde and Ottosen, 1980). Although may serologic methodsare currently available, their limited specificity has restricted their wider usein diagnosis and epidemiologic studies (world health organization, 1980).

Treatment:-

The recent development of praziquantel seems to provide the drug of choicefor the treatment of schistosomiasis in man.

Generally the therapy of animal schistosomiasis has followed that for thetreatmentof human infections, but great care must be taken since veryvariable results have been obtained. Many of the drugs kill the adultschistosomes en masse and theses then become emboli in the portal veins;portal occlusion and hepatic infarction may result and hepatic failure mayoccur. The treatment of cattle infected with S.mattheei has been discussed byLawrence (1978a). Tartar emetic, antimosan and stibophen have beeneffective in the treatment of S.mattheei in cattle but their use has beenassociated with deaths among the treated animals. However, stibophen, thesodium salt of antimosan, was very effective in cattle at a dose rate of 7.5mg/kg given daily for six days. Lucanthone is also effective in the treatmentof S.mattheei in both cattle and sheep; 30mg/kg given on three alternatedays was effective in cattle and moderate efficacy. Was seen when sheepreceived 30-50 mg/kg for three days.

Hycanthone has been used to treat sheep and an intramuscular injection of 3mg/kg was moderately effective while 6mg/kg was highly effective. Inaddition, niridazole was effective insheep at a dose rate of 100mg/kg forthree days. Very variable results have been obtained when trichlorophon hasbeen used to treat infected cattle and sheep. Thus, trichlorophon waseffective against S.bovis in cattle when 50-70mg/kg was given orally on fourto six occasions at three-days intervals. However, 75mg/kg was highly toxicin some treated cattle infected with S. Mattheei. The lack of preparatorystarvation of the animls in the latter experiment may have affected thetoxicity.

Control:-

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

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Biological control has proved effective experimentally but has not yet beenshown to be effective in the field. The larval stages of Echinostoma spp. Arepredatory on schistosome larvae within the snail intermediate host. However,the definitive host of echinostomes are limited in their distribution whichmakes their use in nature impractical. Microsporidial protozoa such asNosema 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. Alsocontract between man and animals and snail-infested water should beprevented. The fencing off of lakes and pools and the provision of pipeddrinking water to troughs aid in preventing infection in animals. In addition,water troughs should be mechanically cleaned periodically. The molluscanintermediate hosts of schistosomes prefer slow-moving or stationary water,so that an increase in the speed of water in irrigation channels will reduce thesnail populations.

The education of humans at risk, the provision of sanitary facilities and theprovision of piped water to houses, laundry units and swimming poolsreduces human contact with contaminated water.before night soil is allowd tocontaminated water it should be treated by fermentation for 25-45 days. Theheat created is sufficient to kill schistosome eggs. When contact with watercannot be prevented, since farmers and other workers may have to enterwater as part of their livelihood, these workers should be provided withprotective clothing. Also, repellants such as dibutylphthalate and benzylbenzoate applied to exposed skin may be effective in preventing penetrationby schistosome miracidia.

Reference:

1- E. J. L. Soulsby (1982) Trematoda Rudolphi .Helminths, Arthropods andprotozoa of Domesticated animals ., 72-80.

2- Pedro N. Acho and Boris Szyfres ,schistosomiasis, zoonosis and communicablediseases 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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Schistosomiasis Amgad.2008journalWNSZ (Recovered)