Nematoda: Understanding Roundworms and Their Life Cycle

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BSMT 101

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Biology

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Dec 12, 2024

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2NDSEMESTER: PARASITOLOGYMODULE 2: Phylum NematodaNote:Nematoda is also known as “roundworms”Estimated 500,000 species of nematodesNematodes are considered parasites anddisease-causing to animals, plants, andhumansHelminth – parasitic wormGENERAL MORPHOLOGYNonsegmented (walang hati/not divided)Generally cylindrical (pabilog)Bilaterally symmetrical (appears the same whendivided in the middle)Tapered at both endsCovered by cuticle (a tough protective coveringmade up of chitin)Complete digestive tract (with oral and analopenings)No circulatory systemSexes are separate (generally males are suchsmaller than female worms)Majority are free-livingDIVIDED INTO 2 CLASSES BASED ON THE PRESENCEOF CHEMORECEPTORSClassPhasmedia–possesscaudalchemoreceptors called phasmids(posteriordepressions used for sensing chemicals in water)ClassAphasmedia–lackscaudalchemoreceptorsExamples: Trichinella, Trichuris, CapillariaSome nematodes also possess anterior orcephalic sensory organs called asamphids(anterior depressions used for sensing chemicalsin water)The appearance of the esophagus also confersterms for the nematodes oFilariform– esophagus is uniformthroughout; noninfective stageoRhabditiform– esophagus expandsposteriorly into a bulb with a valvemechanism; infective stageNematodes have longitudinally oriented musclesimportant for locomotion. There are three types ofmusculature of nematodes:oPolymyarian – more five rows of cellsoMeromyarian – between two to fiverowsoHolomyarian – less than two rowsFemale nematodeshave two cylindrical ovaries,uteri, a vulva, and vaginaMale nematodes may either possess:oA pair of copulatory spiculesoThin-walled copulatory bursa supportedby thickened raysLIFE CYCLEEgg -> Larva -> Adult-Eggs vary in size and shape-LarvaoRhabditiform larva is the stage thathatches from the eggoLarva undergo several molts until itreaches the third stage larva which is thefilariformoFilariform larvae generally characterizesthe infective forms of the parasiteAdult worms have separate sexes. They are alsoequipped with a digestive and reproductivesystemMODES OF TRANSMISSIONThe parasitic nematodes can be transmitted tohumans and animals in a variety of ways:IngestionEmbryonated egg/ova (from contaminated food,drinks, or unwashed hands)Ascaris lumbricoidesTrichuris trichiuraEnterobius vermicularisLarvaCapillaria philippinensisAngiostrongylus cantonensisTrichinella spiralisSkin penetrationStrongyloides stercoralisHookwormsInhalationEnterobius or E. vermicularisTransmammaryStrongyloides or S. stercoralisAncylostoma duodenaleVectorsFilarial wormsINTESTINAL NEMATODESAscaris lumbricoidesCommon name:Gian intestinal roundwormMost common intestinal nematodeLargest intestinal roundwormThe requirement for high temperature and highhumidity confinesdistribution of Ascaris totropical and subtropical regions onlyLife span: Ascaris adult is not a long-lived wormand usually dies in about a yearSoil-transmitted Helminth (STH)like Trichuristrichiuria and hookworms which means that thesoil plays major role in the developmental andtransmission of parasiteFinal host: manHabitat: small intestineIt causes varying degrees of pathology:oTissue reaction to invading larvaeoIntestinal irritation to the adultsoOther complication due to heavy infectionand extraintestinal migrationDisease of the poverty, malnutrition andimpairment of cognitive performance, reducework capacity and productivity of adultsParasite BiologyADULTHas a “polymyarian type”of somatic musclearrangement in which cells are numerous andproject well into the body cavity (also irregularlyarranged)Whitish or pinkish in colorHave a terminal mouth with three lips andsensory papillae (in tongue)Resides in but do not attach to the mucosa ofsmall intestinesLarval morphology is similar to adultMales:o10 – 31 cmoHave ventrally curved posterior end withtwo spicules (needle-like structure)oHave single, long tortuous tubuleFemales:o22 – 35 cm

oHave paired reproductive organ in theposterior two-thirdsoWith smooth striated cuticlesIt has been shown to produce pepsin inhibitor 3(PI 3) that protects worms from digestion andphosphorylcholine that suppresses lymphocyteproliferationINFERTILE OR UNEMBRYONATED EGGMeasures 88 μmto 94 μmby 39 to 44 μm,longer and narrower than fertile eggsThin shell and irregular mammillated coating filledwith refractile granulesMay be difficult to identify and are found not onlyin the absence of malesThey are found in about two of five infectionsFERTILE OR EMBRYONATED EGGSMeasures 45 μmto 70 μmby 35 μmto 50 μmThere is an outer, coarsely mammilatedalbuminous covering which may be absent or lostin “decorticated” eggsThick, transparent, hyaline shell with a thick outerlayer as a supporting structureINFECTIVE STAGE AND FULLY EMBRYONATED EGGHatch in the lumen (opening) of the smallintestine, releasing the larvaeThe larvae then migrate to the cecum or proximalcolon where they penetrate the intestinal wallThese larvae enter the venules to go to the liverthrough the portal vein, on to the heartandpulmonary vessels where they break out ofcapillaries to enter the air sacsIn the lungs, larvae undergo molting beforemigrating to the larynx and oropharynxto beswallowed into the digestive tract Hepato-tracheal migration phase takes about 14days, while the development of egg-laying adultworms takes about 9-11 weeks after egg ingestionLife span of an adult worm is about 1 yearLife Cycle of Ascaris lumbricoidesPathogenesis and Clinical ManifestationMajority of Ascaris infections are asymptomatic(no symptoms)Includes reaction of tissues to invading larvae,irritation of the intestine by the mechanical andtoxic action of the adult, and complications arisingfrom the parasite’s extraintestinal migrationDuring lung migration, larvae may cause hostsensitization resulting in allergic manifestationssuch as:oLung infiltrationoAsthmatic attacksoEdema of the lipsSymptoms of difficulty of breathing and feversimilar to pneumonia may occurMost frequent complaint of patients is vagueabdominal painoEosinophilia (too much eosinophil)oModerate infections may produce lactoseintoleranceoVitamin a malabsorptionHeavy infections are likely to cause:oBowelobstruction(duetobolusformation)oIntussusception(enfoldingofonesegment of the intestine within another;abdominal pain)oVolvulus that may result in bowelinfarction and intestinal perforationSerious, and at times, fatal effects of ascariasisare due to erratic migration of adult wormsoIt may be regurgitated and vomitedoMay escape through the nostrils oInhaled into the tracheaoWorms may invade bile ducts throughampulla of Vater and enter thegallbladder or liveroMay also lodge in the appendix orpancreatic duct which can cause acuteappendicitis or pancreatitisoMay produce abscess (nana)oMay cause acute peritonitis (swelling ofabdomen)DiagnosisDirect Fecal Smear (DFS)– less sensitivecompared to the Kato thick Smear and Kato-KatztechniquesKato thick SmearKato-Katztechniqueprovidesquantitativediagnosis in terms of the intensity of helminthinfection and monitoring of efficacy of treatmentFormalin-ether/ethylacetateConcentrationtechnique (FECT)– higher sensitivity anddetection rate for intestinal parasite infectionTreatmentAlbendazole - given at 400 mg single dose (200 mg for children 12-23 months)Mebendazole - 500 mg single dose Pyrantel pamoate - 10 mg/kg (max. 1 g) also as a single oral dose Preventive chemotherapy - done through mass drug administration (MDA) with anthelminthics Integrated Helminth Control Program (IHCP) ofDOH conducted every January and JulyWomen of the child bearing age and pregnantwomen may receive albendazole or mebendazoleDeworming in the school age group includingimprovement in iron stores, growth and physicalfitness, cognitive performance and schoolattendanceEpidemiologyAscaris has a cosmopolitan in distributionChildren ages 5-15 years have the highest intensities of infection with ascaris compared withthe other age groupsChildren are particularly vulnerable due to risk of ingesting embryonated egg while playing in soil

In many low and middle income countries like thePhilippines, the prevalence may reach 80 to 90%in certain high risk groups like public elementaryschool children The level of transmission of Ascaris and other STHfrom soil to humans depends on socio-economicfactors more than on physical factorsThe main factors appear to be:oA high density of human populationoInvolvement in agriculture (including useof night-soil as fertilizer)oIlliteracy and poor sanitationoPoor health educationPrevention and ControlSurveillance and monitoring are important components of an STH Control ProgramKato-Katz method is usedDewormingNutritional status and school performanceProvision of safe water, environmental sanitation, hygiene educationRegular dewormingMass treatmentTrichuris trichiuriaCommon name:Whipworm and is a soil-transmitted helminthClassified as holomyarian, based on the arrangement of somatic muscles in cross-section where the cells are small, numerous, and closely packed in a narrow zoneLife span: 4-8 yearsOnly one host: manHabitat:Large intestineInhabits the cecum and the colonThe worms secrete a pore-forming protein, calledthe TT47 that allows them to imbed their entirewhip-like portion into the intestinal wall Parasite BiologyADULTMale worm:o30-45 mmoHas a coiled posterior with a single spicule and retractile sheathFemale worm:o35-50 mmoHas a blunt posterior endEGG50-54 μmby 23 μmIt is lemon or football-shaped with plug-like translucent polar prominencesYellowish outer and transparent inner shellFERTILIZED EGGUnsegmented at oviposition and embryonicdevelopment takes place outside the host wheneggs are deposited in clayish oilMore susceptible to desiccation (madaling kapitanng pagkatuyo) than ascaris eggsLARVAEEscape and penetrate intestinal villi where theyremain for 3-10 day soon after the embryonatedeggs are ingestedLife Cycle ofTrichuris trichuriaPathogenesis and Clinical ManifestationThe anterior portions of the worms, which areembedded in the mucosa,cause petechialhemorrhages, which may predispose to amebicdysentery, presumably because the ulcers providea suitable site for tissue invasion by E. histolytica The lumen of the appendix may be filled withworms,andconsequentirritationandinflammationmay lead to appendicitis orgranuloma formationIn patients with heavy intensity infection, theworms may be found throughout the colon andrectum, and may result in Trichuris dysenterysyndrome manifested by chronic dysentery andrectal prolapseCases of heavy chronic trichuriasis are oftenmarked by:oFrequent blood streaked diarrheal stoolsoAbdominal pain and tendernessoNausea and vomitingoWeight lossAnemia is strongly correlated to heavy intensitytrichuriasis Trichuriasis has also been shown to result in poorappetite, wasting, stunting, as well as reducedintellectual and cognitive development in childrenBecause there is no larval migration through thelungs as in Ascaris and hookworm infections, nolung pathology occursDiagnosisClinical diagnosis is possible only in very heavychronic Trichuris infection patientsuffers fromfrequent blood-streaked diarrhea, abdominal painand tenderness, and rectal prolapse where adultworms attached to the rectal mucosa can be seenIn light infections where symptoms are absent,laboratory diagnosis is essentialMay be done by direct fecal smear (DFS) with adrop of salineAn alternative diagnostic technique is the Katothick smear method The Kato-Katz techniqueis a quantitative methodthat employs egg counting to determine theintensity of helminth infectionTheacid-ether and the formalin-ether/ ethylacetate concentration techniquescan also beused for the diagnosis of trichuriasisThe FLOTAC techniquehas also been shown to bemore sensitive in the diagnosis of trichuriasiscompared with Kato-Katz and ether/ethyl acetateconcentration techniquesTreatmentMebendazole- given 100 mg twice a day for 3 daysAlbendazole– alternative drug

Both are benzimidazole derivatives and areavailable as chewable tablets. Administration ofmebendazole 500 mg once a day for 3 days hasbeen shown to have the highest cure rate (71%)compared with albendazole 400 mg given once aday for 3 days (56%)Dewormingof children has been shown tocontribute to improved motor and languagedevelopment, as well as to reduced malnutritionEpidemiologyOccurs in both temperate and tropical countriesbut is more widely distributed in warm, moistareas of the worldMost prevalent in East Asia and Pacific Islandregions, and least prevalent in the Middle Eastand North African regionsAmong the different age groups, children 5 to 15years of age are most frequently infected, andhave the highest intensities of infectionPrevalence of co-infections with the two helminthsis 19.1% in a recent sentinel surveyPrevention and ControlSimilar to those for Ascaris infectionsWHOrecommendsbiannualmassdrugadministration with mebendazole 500 mg oralbendazole 400 mg among school-age children incommunities where the prevalence of STHinfections is ≥50%Treatment of other high-risk groups such aspreschool children, women of childbearing age,including pregnant women in the 2nd and 3rdtrimesters as well as lactating women, adults incertain high-risk occupations should also beconsidered HookwormsNecator americanus and Ancylostoma duodenale,which are soil-transmitted helminthsBlood-sucking nematodes that attach to themucosa of the small intestinesMost commonly found in tropical and subtropicalcountries where they occur as single or mixedinfections Parasite BiologyAll hookworms have the meromyarian typeofsomatic muscle with two to five cells arranged perdorsal or ventral halfN. americanusadults are small, cylindrical,fusiform, grayish-white nematodes Buccal capsule has a ventral pair of semilunarcutting platesThe head is curved opposite to the curvature ofthe body, which is like a hook at the anterior end Female:o9-11 mm by 0.35 mm Male:o5-9 mm by 0.30 mmoHas a broad, membranous caudal bursawith rib-like rays, which are used forcopulationLife Cycle of HookwormPathogenesis and Clinical ManifestationPathology of hookworm infection involves:oThe skin at the site of entry of thefilariform larvaeoThe lung during larval migrationoThe small intestine, the habitat of theadult wormsPenetration of the filariform larvae through theskin produces maculopapular lesions and localizederythemaItching is often severe, and it is known as “grounditch” or “dew itch,” as it is related to contact withsoil, especially on a dewy morningChronic moderate or heavy hookworm infectionresults in a progressive, secondary, microcytic,hypochromic anemia of the iron-deficient type,due primarily to continuous loss of bloodHypoalbuminemiais another manifestation ofhookworm infection. There is low level of albumindue to combined loss of blood, lymph, and proteinDiagnosisFinal diagnosis depends on the identification ofparasite ova in the feces. The following techniques areinexpensive and can be applied to both individual andmass screening: Direct fecal smearis of value only when theinfection is quite heavy. It may not detect theparasite in light infections The Kato thick or Kato-Katz methodmay increasedetection rates since more stools are examinedusing these techniques. The latter technique mayalsoprovidequantitativediagnosisbydetermining the intensity of infection in terms ofnumber of helminth eggs per gram of feces. Thedisadvantage of these methods is the rapidclearance of hookworm eggs after 30 to 60minutes with the use of glycerine as a clearingagent Concentrationmethodslikezincsulfatecentrifugal flotation and the formalin-ether/ethylacetate concentration methoduse greaterquantity of stool that may contribute to theincrease in sensitivity. FLOTAC, which is also acentrifugal flotation method, has been shown tohave a higher sensitivity for the diagnosis of soil-transmitted helminths compared with multipleexaminations of Kato- Katz smears Culture methods like the Harada-Moriallowhatching of larvae from eggs on strips of filterpaper with one end immersed in water. Culturemethodsarerecommendedforspeciesidentification Molecular approaches, which include PCR-baseddetection of hookworm DNA in fecesand enzyme-linked immunosorbent assay (ELISA)for the

detection of secretory/excretory coproantigens,have also been developedTreatmentIf the risk of reinfection is high, mass screeningbefore treatment may be impractical. WHOrecommends mass drug administrationamongschool-age children at least once a yearAlbendazole, the drug of choice, is larvicidal andovicidal against N. americanus and A. duodenale.It is given as a 400 mg single dose for adults andchildren over 2 years old Mebendazolefor children and adults is given as a500 mg single dose. These drugs are bothbenzimidazole derivatives that block the uptake ofglucose by most intestinal and tissue nematodes Anemia and hypoproteinemia should also beaddressed by giving iron supplementationandadequate diet EpidemiologyA. duodenalewas prevalent in Europe andSouthwestern Asia, while N. americanus wasprevalent in tropical Africa and the Americas But now, both species have become widelydistributed throughout the tropics and subtropics,and rigid demarcations are no longer present In the Philippines, local studies on speciation ofhuman hookworms revealed that out of 1,958samples positive for hookworm in cultures, 97%were identified as N. americanus, 1% as A.duodenale, and 2% were mixed infections The local distribution of human hookworminfection is greater in agricultural areas. Farmersare prone to the infection because they work inrice fields and vegetable gardens, and they arenot properly protected from contact with infectivesoilRecent surveillance in sentinel sites in thePhilippines revealed an overall prevalence ofhookworm infection at 1.1% and 1.9%forpreschoolchildrenandschoolchildren,respectively Among pregnant women and adolescent females,the prevalence rates are 5.5% and 2.8%,respectivelyFactors that contribute to the distributiona.Suitability of the environment for eggs or larvae:damp, sandy or friable soil with decayingvegetation, and temperature of 24 to 32°Cb.Mode and extent of fecal pollutionof the soil(through open defecation or the use of night soilas fertilizer)c.Mode and extent of contact between infected soiland skin or mouthWhereas the method of human infection in:oNecatoriasis– purely percutaneous,oAncylostomiasis– both percutaneous andthrough the oral routeThere are also animal hookworms likeAncylostoma braziliense (cat hookworm)andAncylostoma caninum (dog hookworm)that caninfect humans causing “creeping eruption,” alsoknown as cutaneous larva migrans (CLM)Prevention and ControlRegular mass drug administrationin schools aspart of the national control program had resultedto a decrease in the prevalence of soil-transmittedhelminths among school children in a number ofareas in the PhilippinesCoverage of dewormingis limited to preschool-and school-age children, leaving other high-riskgroups vulnerableIn the Philippines, the WASHED approachis beingadvocated for a more comprehensive control ofSTH infections. This approach refers toimprovement in access to clean water andsanitation, promotion of hygiene education, andregular dewormingOpen defecationshould be discouraged andsanitary disposal of human feces, as well aswearing of shoes, slippers, and boots should beadvisedStrongyloides stercoralisCommon name:Thread wormSmallest nematode of a manCapable of heart-lung migrationLife span: Ascaris adult is not a long-lived wormand Only one host: manHabitat: small intestineModeofliving:facultative(free-livingrhabditiform or parasitic filariform stages)STHOnly species of this genus which is naturallypathogenic to humansParasite BiologyADULTParasitic or filariform femaleo2.2 mm by 0.04 mmoColorlessSemi-transparent with a finely striated cuticleoWith slender tapering anterior end and short conical pointedoNon-feeding slender with distinct cleft at the tip of the tailFree-living femaleo1 mm by 0.06 mm and smaller that parasitic femaleoHas muscular double-bulbed esophagusoIntestine is a straight cylindrical tubeFree-living maleo0.7 mm by 0.04 mmoSmaller than the femaleoHas a ventrally curved tail, two copulatory spicules, a gubernaculum, but no caudal alaeEGGHave clear thin shellSimilar to those of hookworms except that they measure only about 50-58 μmby 30-34 μmFREE-LIVING FORMSFound in the soilFemale worm lays embryonated eggs, whichdevelop into rhabditiform larvae after few hours

These larvae feed on organic matter andtransform into free-living adults Autoinfection occurs when rhabditiform larvaepass down the large intestine and develop intofilariform larvae. Being the infective stage, thesefilariform larvae may invade the mucosa andenter the circulation to start another parasiticcycle without leaving the body of the host Life cycle of Strongyloides stercoralisDiagnosisThe application ofrepeatedconcentrationtechniques,liketheBaermannfunnelgauzemethod, usuallyleads to detectionof the infection Harada-Moricultureis considered one of the most successfulmethods in parasite identification Other laboratory methods that can be done areBeale’s string test, duodenal aspiration, and smallbowel biopsy TreatmentAll infected individuals should be treated.Treatment was previously based on albendazoleor thiabendazole Recent studies show that ivermectinalso providesthe best results in chronic uncomplicatedstrongyloidiasis with regard to efficacy andtolerability. Higher doses given for longer periodsmay be necessary Albendazole, thiabendazole, and ivermectinhavebeen used to treat hyper infection ordisseminated disease singly or in combination,but data are limited to case reports or case series Albendazoleandthiabendazolearecontraindicated in pregnant women and in thosewith known hypersensitivity to the drugs EpidemiologyIn the Philippines, strongyloidiasis is relativelyrare Infection and disease rates as well as morbidityand mortality figures are not well documented.The factors that affect transmission include poorsanitation and indiscriminate disposal of humanfeces that may contain Strongyloides larvaePrevention and controlPrevention and control measures for this diseaseare similar to those for hookworm infection. Bothworms use the soil for further development andmaintain their endemicity in areas whereenvironmental sanitation is poor and human fecesis deposited indiscriminately in the soil byinfected peopleThere is a need to provide health education onpersonal, family and community hygienetochange behavior and practices Enterobius vermicularisCommon name:Pin worm, society worm, seatwormMost common helminth parasite of temperateregions and crowded indoor livingLife span: one to two monthsOnly one host: manHabitat: large intestine (cecum)Human pinworm that causes enterobiasis oroxyuriasis. The infection is typically characterizedby perianal itching or pruritus aniNot a usual cause of significant morbidity ormortality, migrating worms may go beyond theperianal region and can occasionally causecomplicationsinectopic areas Classifiedasmeromyarian, basedon the arrangementofthesomaticmuscles where thereare two to five cellsper dorsal or ventralhalf Mostcommonhelminthparasiteidentifiedintemperateregions,whereenvironmental sanitation is in placeParasite BiologyADULTHave cuticular alar expansions at the anterior endand a prominent posterior esophageal bulbGravid female worms migrate down the intestinaltract and exit through the anus to deposit eggs onthe perianal skinAdult female worms migrate to the perianal area,usually in the evening hoursA single female lays from 4,672 to 16,888 eggsper day with an average of 11,105 eggsAfter egg deposition, the female usually dieWhen ingested, eggs containing the 3rd stagelarvae hatch in the duodenum, pass down thesmall intestines to the cecum, and develop intoadultsSmall adult female worm:o8-13 μmby 0.4 μmoHas a long pointed tailoUteri of gravid females are distended witheggsMale:o2-5 mm by 0.1-0.2 mmoHas curved tail and a single spiculeoRarely seen because they die aftercopulationRHABDITIFORM LARVA140-150 μmby 10 μmHas the characteristic esophageal bulb but has nocuticular expansion on the anterior end

EGGSAsymmetrical, with one side flattened and theother side convex50-60 μmby 20-30 μmin size averaging 55-36μmThe translucent shell consists of an outer triplealbuminous covering for mechanical protectionand an inner embryonic lipoidal membrane forchemical protection Inside the egg is a tadpole like embryo thatbecomes fully mature outside the host within 4 to6 hours Life cycle of Enterobius vermicularisPathogenesis and Clinical ManifestationEnterobius vermicularis is relatively innocuousparasiteand rarely produces any serious lesions Mild catarrhal inflammationof the intestinalmucosa may result from the attachment of theworms Mechanical irritation and secondary bacterialinvasionmay lead to inflammation of the deeperlayers of the intestines Invasion of the appendix is not unusual, butwhether this invasion is a significant cause ofappendicitis is not known Migration of egg-laying females to the anuscauses irritation of the perineal regionComplications such as appendicitis, vaginitis,endometritis, salpingitis, and peritonitis are alldue to aberrant adult worm migration Entry into the peritoneal cavity via the femalereproductive system may result in the formationof granuloma around eggs or worms DiagnosisEnterobiasis should be suspected in children andadults who show perianal itching relieved only byvigorous scratchingDiagnosis is confirmed by finding adult worms oreggs on microscopic examinationsAdult worms may be seen in the fecesor in theperianal region Eggs are found in the fecesin only about 5% ofinfected persons The method of laboratory diagnosis is theGraham’s scotch adhesive tape swab (perianalcellulose tape swab), which gives the highestpercentage of positive results, and the greatestnumber of eggs seen. This low-cost diagnosticmethod is easy to perform and is very sensitiveand specificEpidemiologyEnterobiasis occurs in both temperate and tropicalregions of the world, and has a high prevalence inboth developed and developing countries It is the only intestinal nematode infection thatcannot be controlled through sanitary disposal ofhuman feces, because the eggs are deposited inthe perianal region instead of the intestinal lumenEggs usuallycontaminate underwear andbeddingsThe route of infection is through the mouth, therespiratory system(by inhalation of dustcontaining Enterobius eggs), and through theanus (wherein the hatched larvae enter the anusand cause retroinfection when they go back intothe large intestine) Risk factorsfor infection include overcrowding,thumb-sucking, nail- biting, and lack of parentalknowledge on pinwormsPrevention and controlPersonal cleanlinessand personal hygiene areessential Fingernails should be cut shortand hand washingshould be done after using the toilet, as well asbefore and after meals The use of showersrather than bathtubs issuggested, and infected persons should sleepalone until adequately treatedUnderwear, night clothes, blankets, and bedsheets should be handled with care and washed inhot soapy water Vacuum cleaning around beds and contaminatedareas will be useful The implementation of mass drug administrationtargetingsoil-transmittedhelminthiasesisexpected to have an impact on the prevalence ofenterobiasis as well Capillaria philippinensisCommon name:Pudoc wormBelong to the superfamily TrichinelloideaNatural host: Migratory birds (fish-eating)Final host: manHabitat: small intestineOne of four Capillaria species that are known toinfect humans Intestinal capillariasis, a zoonotic disease(animal-transmitted), is characterized by abdominal pain,chronic diarrhea, and gurgling stomach. Thedisease may also be associated with protein-losing enteropathy, electrolyte imbalance, andintestinal malabsorptionParasite BiologyCapillaria philippinensis is a nematode from thesuperfamily Trichinelloidea, to which Trichuris andTrichinella belong The parasites in this superfamily characteristicallyhave a thin filamentous anterior end and a slightlythicker and shorter posterior endThe esophagus has rows of secretory cells calledstichocytes, and the entire esophageal structureis called a stichosome

The anus is subterminal, and the vulva in femalesis located at the junction of anterior and middlethirdsFemale worms produce characteristic eggs, whicharepeanut-shaped with striated shells andflattened bipolar plugs These eggs, which measure 36-45 μmby 20 μm,are passed in the feces and embryonate in thesoil or waterFish-eating birds are believed to be the naturalhostsof C. philippinensis, andhumansareconsidered incidental hostsLife Cycle of Callaria philippinensisPathogenesisandClinical ManifestationPersons with C. philippinensis usuallyhaveabdominal pain and borborygmi Patients initially experience intermittent diarrhea,which progresses to passing out8 to 10voluminous stools per day Laboratory findings show severe protein-losingenteropathy and hypoalbuminemia;oMalabsorption of fats and sugarsoDecreased excretion of xyloseoLow serum potassium, sodium andcalciumoHigh levels of immunoglobulin E The parasites do not invade intestinal tissue, butthey are responsible for micro-ulcers in theepithelium, and the compressive degenerationand mechanical compression of cells DiagnosisDiagnosis is based on finding characteristic eggsin the feces by direct smear or wet mount, as wellas by stool concentration methodsThere may also be various larval stages of theparasites, as well as adult worms in the fecesThe parasites can also be recovered from thesmall intestines by duodenal aspirationA study done in Egypt demonstrated highspecificityofsandwichenzyme-linkedimmunosorbent assay (ELISA)in the detection ofcoproantigen prepared from stool samples ofpatients with capillariasis TreatmentIn severe cases with electrolyte and protein loss,patients should be given electrolyte replacementand a high protein diet The drug of choice for the treatment of intestinalcapillariasis is mebendazole, 200 mg twice a dayfor 20 days Alternatively, albendazole400 mg may be givenonce daily for 10 days EpidemiologyIntestinal capillariasis was first recorded inNorthern Luzon in the Philippines. In 1966, anepidemic in Pudoc West, Tagudin, Ilocos Surwasreported, that spread to neighboring towns andresulted in more than 1,000 cases and 77 deathsInfections are acquired by eating uncooked smallfreshwater/brackish water fish. Ilocano peopleenjoy eating bagsit and other fishes found in thelagoons In Monkayo,Compostela Valley Province, anoutbreak described as a “mystery disease” in1998 resulted in the death of villagers due tomisdiagnosis Prevention and ControlIt is believed that the 1967 to 1968 Philippineepidemic was due to washing of fecallycontaminated bed sheets in lagoons in theTagudin area of Ilocos SurEfforts to improve sanitation and healtheducational programs to prevent indiscriminatedisposal of human waste and to discourage eatingraw fish are important in controlling the spread ofinfection Capacity building for health personnel in the field,including laboratory staff, for early and accuratediagnosis and treatment is important inpreventing mortalityHealth education can also help improve patienthealth-seeking behaviors