Medical Parasitology PDF

Introduction to Immunology parasitology: area of biology concerned with the phenomenon of dependence of one living organism on another medical parasitology: concerned primarily with parasites that affect humans and their medical signi cance as well as their importance in human communi...

Introduction to Immunology parasitology: area of biology concerned with the phenomenon of dependence of one living organism on another medical parasitology: concerned primarily with parasites that affect humans and their medical signi cance as well as their importance in human communities tropical medicine tropical disease: illnesses that is indigenous to a tropical area but may occur in sporadic or epidemic proportions in areas that are not tropical (many are parasitic) symbiosis: living together of unlike organisms that involve protection or other advantages to one or both organisms (commensalism, mutualism) parasitism: one organism lives or on another depending on the latter for its survival and usually at the expense of host (endoparasite, ectoparasite) - obligate parasites: host is needed at some stage of their life cycle to complete their dev't and to propagate their species - facultative parasite: may exist in a free-living state or may become parasitic when need arises - accidental or incidental parasite: establishes itself in host where it does not normally live - spurious parasite: free living organism that passes through the digestive tract without infecting the host hosts: - de nitive or nal host: one in which parasite attains sexual maturity - intermediate host: harbors asexual or larval stage of parasite - paratenic host: parasite does not develop further to later stages; remains alive and is able to infect another susceptible host vectors: responsible for transmitting parasite from one host to another fi fi fi  modes of transmission: - foodborne - skin penetration - bites of arthropod vectors - congenital transmission - inhalation of airborne eggs - sexual intercourse simple or complicated: perpetuation of species of parasite depends upon ability to ensure transmission from one host to next -> parasite must adapt to protect itself from host's defenses and external environment; parasite must overcome attrition by producing numerous progeny Terminologies life cycle: infective and diagnostic stages, mode of transmission: many parasites have a single host, being transferred from one individual to another of the same species either through direct physical contact or by means of resistant or semi-resistant forms that are able to survive a period outside or away from host - encysting protozoans: infective stage is called cyst - non-encysting protozoans: infective stage is called trophozoite - egg laying nematodes: infective stage is called embryonated egg vector-transmitted parasites: - vector may be host if dev't of parasite takes place within its body - if arthropod is simply an instrument of passive transfer, we refer to it as mechanical vector (ex. y transfers fecal matter containing cysts of E. histolytica to food) - when anopheline mosquito sucks blood from malaria patient, parasite must develop in mosquito before it is able to transmit infection (mosquito is both host & biological vector) life cycle - refers to dev't of parasite in its earliest form and its survival and dev't in the outside environments and within host - may be simple or complex (invovles two or most hosts) epidemiology: occurence and distribution of disease in human population and communities; even though treatment, prevention and control measures are available, parasitic infection still occurs and thus it is important to study and monitor trends prevalence: statistical study referring to number of cases of a disease that are present in a particular population at a given time incidence: number of new cases that develop in a period of time fl  distribution of disease: - endemic: disease maintains relatively steady, moderate level - epidemic: sharp rise in incidence - hyperendemic: prevalence of disease is high - sporadic: appears only occasionally - pandemic control, prevention and treatment: - preventive control measures may be taken against every parasite that is infective to humans; designed to break transmission cycle - preventing infections to happen is to intervene in life cycle of parasite and prevent successful entry of infective stage to host - parasitic treatment options: antiparasitic medication & therapies option elimination vs eradication - elimination: its transmission is no longer active in a certain area - eradication: worldwide transmission of it is over w no remaining cases disease control in local setting is rst step; experts use deliberate and continued efforts to lower rates of new infections, deaths and current infections in one region fi Zoonotic Parasites any disease passed from animals to people or vice versa 60% of human pathogens are zoonotic 75% of emerging infectious diseases have animal origin causes of zoonotic disease: ○ bacteria ○ fungi ○ virus ○ parasites many methods of transmission to people involve animals vector-borne parasites: ○ vector: agent that transfers parasite from one host to another ○ mosquitoes, ticks, eas, mites and other insects ○ vector picks up parasite from animal -> human parasites carried by vectors: found in blood of humans and animals ○ Trypanosoma cruzi ◆ causes Chagas disease ◆ damage to heart, digestive tract & brain (in children) ◆ spread by "Kissing Bug" (native to South America & Southern US) ◆ bug bites human -> defacates next to wound -> rubbing bite wound spreads parasite into wound ◆ can cycle from animals like armadillos, raccoons, opossums & foxes to bugs to humans ○ Babesia ◆ intracellular protozoa found in RBC ◆ spread via infected ticks ○ Leishmania ◆ live in tissue and not in blood ◆ spread via bite of infected sand y ◆ common in Caribbean beaches fl fl  waterborne parasites: ○ spread via contaminated water ○ common waterborne parasites: ◆ Giardia ◆ Cryptosporidium ○ Giardia & Cryptosporidium ◆ obtained from swallowing contaminated water infected by another human or animal ◆ Giardia is the 2nd most common parasitic disease in humans ◆ Cryptosporidium is the most common cause of diarrhea from swimming ◆ both cause severe diarrhea methods of parasite transmission: ○ insect bite ○ animal feces ○ handling raw meat & sh ○ handling cat litter boxes ○ contaminated fruits and veggies ○ infected food handlers ○ contaminated water ○ contact with infected person modes of transmission: ○ vectorborne ○ waterborne ○ fecal-oral transmission ◆ most common way; parasites are spread to humans when they ingest egg from feces of animal; generally live in intestinal tract (hookworms, roundworms, hydatid disease, toxoplasmosis) ○ contaminated meat fi  hookworms & roundworms ○ carried by dogs and cats ○ kids are often infected from sand boxes where animals defacate or by putting toys in mouth from ground ○ hookworms: ◆ can penetrate skin and gain entry into human body ◆ bare feet are a common route of entry ○ hydatid disease: ◆ after humans consume eggs passed by dogs the worms can form huge cysts in the body ○ toxoplasmosis ◆ pregnant women shouldn't clean litter boxes; possible to lose unborn child ◆ can be transmitted via uncooked meat ◆ 3rd leading cause of foodborne related deaths in the US contaminated meat ○ common parasites: ◆ Toxoplasma ◆ Trichinella ◆ Taenia ◆ Gnathostoma ○ trichinosis & taeniasis ◆ caused by eating cysts in uncooked pork or beef ◆ incidence rate has decrease w better animal management & slaughter protocol ○ cysticercosis: obtained from eating Taenia eggs; cyst form in the brain ○ gnathostomosis: found in raw sh; most common in Asia fi Protozoan Infections Entamoeba histolytica classi ed within subphylum sarcodina, class lobosea, order amoebida pseudopod-forming non agellated most invasive and causes colitis (in ammation of colon) and liver abscess (fatal) life cycle: ○ infective cyst & invasive trophozoite (can travel from one tissue to another) no host other than humans life cycle: ○ humans accidentally ingests cysts ○ amoeba can exit body as trophozoite/cyst form ○ trophozoites are short-lived once in environment ○ only cysts could reach humans once again ○ ingestion of cysts -> excystation in small intestine (can be asymptomatic colonization, invasive or producing liver abscess) -> division of quadrinucleate cyst into 4 and then 8 trophozoites -> trophozoites move to colonize colon -> encystation -> excretion of cysts -> ingestion of cysts by patient prevention and control of amoebiasis: ○ improve environmental sanitation ○ provide sanitary disposal of human feces ○ safe drinking water & food free living pathogenic amoebae (Acanthamoeba) exist as free living organisms in nature occasionally invade a host and live as parasites within host tissue characteristics: fi fl fl  active trophozoite stage and dormant cyst stage reproduce via binary ssion and encyst if the environment is unfavorable ubiquitous (found in aquatic environments even water bottles) causative agent of granulomatous ameboc encephalitis (GAE) and Acanthamoeba keratitis simple life cycle (only needs humans to complete life cycle) cysts & trophozoites enter via: ○ eye ○ nasal passages ○ lower respiratory tract (lungs) ○ broken skin (lesion and wounds) free living pathogenic amoebae (Naegleria) cyst (de nite shape and cyst wall) -> trophozoite (amebic stage) -> agellate stage (swimming form) causes gastritis and diarrhea to a rapidly fatal primary amebic meningoencephalitis (PAM) acquired through oral and intranasal routes via contaminated water can survive elevated temperatures of up to 46 degrees Celsius cyst, trophozoite and agellated form can be found in soil and water water-related activities allow parasite to get in body and eventually reach brain respiratory and brain damage fi fl fi fl parasitic agellate (Giardia lamblia) two nuclei - trophozoite intestinal parasitic agellate of worldwide disitribution cause epidemic and endemic diarrhea GIARDIASIS or LAMBLIASIS which manifests as a signi cant but not life-threatening gastro- intestinal disease found in duodenum, jejenum and upper ileum simple asexual life cycle: binucleated agellated trophozoites & quadrinucleated infective cyst stages cyst can be attached to anything that can be ingested by humans excysted in small intestine and invade tissues Trichomonas vaginalis humans are only hosts TRICHOMONIASIS ○ symptoms among women: ◆ vaginal discharge ◆ vaginal spotting or bleeding ◆ genital burning or itching ◆ genital redness or swelling no cyst stage ◆ frequent urge to urinate ◆ pain during urination or sexual intercourse ○ symptoms among men: ◆ discharge from urethra ◆ burning during urination or after ejaculation ◆ urge to urinate frequently fl fi fl fl MALARIA leading parasitic disease that causes mortality worldwide (most widely in Africa, South America, Central America, Southeast Asia) Plasmodium ○ carried by Anopheles mosquito (P. falciparum, P. vivax, P. ovale, P. malariae) major symptoms: - unarousable coma - acidemia/acidosis - severe normochromic normocytic anemia - renal failure - pulmonary edema/ARDS - hypoglycemia - hypotension/shock - bleeding/disseminated intravascular coagulation - convulsions minor symptoms: - hemoglobinuria - extreme weakness - hyperparasitemia - jaundice diagnosis - peripheral blood smears (thick & thin) - rapid diagnostic tests - ELISA - screening (serologic; measure of intensity) treatment - artemisinin-based combination therapy ( rst line therapy for uncomplicated malaria) - atovaquone-proguanil (second line treatment for important malaria) - chloroquine (used for pregnant patients alongside abct) - armodiaquine fi  - primaquine (for relapse; not allowed for pregnant) - quinine & artesonine (for severe malaria) Plasmodium life cycle Anopheles mosquito feeds on blood & serves as vector sporozoites enter blood stream and proceed to liver within 30 mins to infect hepatocytes 1 week = multiplication & transformation in liver leads to release of about 5k - 10k merozoites per hepatocyte infected w only one sporozite merozites infect red blood cells, initiating the symptoms and pathology of malaria merozites replicate and differentiate cell ruptures to release new merozoites (which infect more rbc) some merozoites differentiate into gametocytes (micro = males & macro = females) gametocytes ingested by female Anopheles differentiate into male and female gametes which fuse to form a zygote and become sporozoites in salivary glands malaria symptoms chills, fever, sweating - peak every 48 hrs weakness, anemia, splenomegaly blocked capillaries - intense headaches, renal failure, heart failure or cerebral damage AFRICAN SLEEPING SICKNESS WEST EAST Trypanosoma brucei ○ agellated protozoans - 2 species ○ tsetse y (Glossina spp.) as carrier multiplies in blood: ○ progresses from neurological stage, infects CNS -> meningoencephalitis ○ loss of consciousness (SLEEP) Leishmaniasis caused by diploid protozoa vector: sandly (Phlebotomus & Lutzomiya) produces amastigotes (ovoid or round bodies) intracellularly in mammmalian host and pro- mastigotes (w single agellum) in hindgut, midgut and proboscis of insect vectors highly endemic: South America and Middle East pathogenesis and clinical manifestations: ○ four categories: ◆ cutaneous leishmaniasis - most common; sore, ulcer ◆ diffuse cutaneous leishmaniasis - numerous diffuse satellite lesions; non- ulcerating ◆ mucocutaneous leishmaniasis - involvement of mucus membranes of nasal and oral cavities resulting to destruction of nasal septum ◆ visceral leishmaniasis - spread of parasites into bone marrow, spleen and liver Coccidians spore-forming, single-celled obligate intracellular protozoan members of Phylum Apicomplexa are provided with cluster of secretory organelles fl fl fl  (rhoptries, micronemes, polar rings w microtubules, conoid) which allows the parasite to enter host cell coccidians infect intestinal tract of invertebrates and vertebrates including humans coccidian life cycle includes alteration of sexual and asexual multiplication ○ 3 sequential stages ◆ sexual cycle or sporogony -> oocysts ◆ asexual cycle or schizogony/merogony -> merozoites/meronts ◆ gametogony -> male (micro) and female (macro) gametocytes (gamonts) Cryptosporidium all stages of dev't are completed in gastrointestinal tract of host oocysts when passed out are already infective each oocyst contains four sporozoites, which are present at time of passage into feces oocyst is infectious and when ingested, sporozoites attach to surface of epithelial cells of GI tract diagnosis: ○ stool examination - reveals oocyst ◆ sheather's sugar otation ◆ formalin ether/ethyl acetate concentration technique (FECT) ◆ kinyoun's modi ed acid-fast stain ○ indirect uorescent antibody, enzyme immunoassay ○ DNA probes speci c for Cryptosporidium hominis ○ acid-fast staining pathogenesis and clinical manifestations ○ diarrhea lasting for 2 to 3 weeks ○ abdominal pain, anorexia, fever, nausea, weight loss ○ villi of intestines become blunted; in ltration of in ammatory cell into laminate propria fl fi fl fi fi fl  and elongated crypts ○ varying degrees of malabsorption; excessive uid loss TOXOPLASMOSIS Toxoplasma gondii ○ coccidian that belongs to Phylum Apicomplexa ○ parasitic w worldwide distribution; infects humans and many species of animals ○ infective stages: tachyzoites, bradyzoite and oocyst ○ life cycle: schizogony, gametogony and sporogony in intestinal epithelium ○ extraintestinal stages are asexual stages: tachyzoites and bradyzoites ○ de nitive host: CAT pathogenesis and clinical manifestations ○ commonly asymptomatic as long as immune system is functioning well ○ cysts can be found in brain, skeletal and heart muscles, retina ○ manifestations: encephalitis, myocarditis, pneumonia, hepatitis, splenomegaly, stillbirth and abortion Sarcocystis spp. intracellular protozoa reported to infect humans and animals worldwide SARCOSPORIDIOSIS or SARCOCYSTOSIS simplest form - zoite (banana shaped cell w pointed anterior end; apical complex w fi fl  micronemes, micropores and rhoptries) humans -> animals -> humans (again) life cycle: ○ merozoites penetrate muscle cells ○ once developed, can be ingested by humans via raw/imporperly cooked meat ○ passed onto intestine and damage via circu- lation to different parts of body ○ fertilization happens and exits host ○ sporocysts and oocysts are passed thru feces ○ crucial: if stages are in soil and animals feed on sporocysts (pig and cow) and ruptures and enters endothelial cells and undergo scyzogony and merozoites penetrate muscle cells and develop into cells w bradyzoites affect movement of animal pathogenesis and clinical manifestations ○ invasive forms: vasculities (in ammed blood vessels) and myositis; may involve wide variety of tissues including lymph nodes, muscles and larynx ○ intestinal form: nausea, abdominal pain, diarrhea ○ other symptoms: anorexia, nausea, abdominal pain, diarrhea, vomiting, tachycardia Babesia spp. hemosporidian parasite causing BABESIOSIS (hemolytic) DH: mammals; IH: ticks (tickborne) life cycle: ○ mammalian hosts merogony in RBC ○ tick vector gamogony in gut and epithelium ○ sporogony accompanied with multiple ssion in various cells and organs forming sporokinete and infective sporozoite fl fi  merozoites form tetrads transferred via blood transfusion within tick: ○ picks up thru blood meal and ingest gametes gamete fertilization happens and enter salivary gland (sporogony) producing sporozoites injected into human or rat host Platyhelminthes LIVER FLUKES Fasciola spp. large digenetic termatodes found in liver and biliary passages of humans and ruminants Fasciola hepatica: temperate liver uke Fasciola gigantica: tropical liver uke life cycle: ○ metacercaria exists in duodenum or jejunum ◆ release juvenile uke that penetrate intestinal wall until peritoneal cavity ◆ wander until it reaches capsule of Glisson (outer layer of liver) and enter liver ○ unembryonated egg carried by bile thru sphincter of Oddie in intestine ○ eggs will mature in water (9-15 days) and transform into miracidium once it exits oper- culum ○ miracidium will look for its rst IH ◆ snail from family Lymnaeidae life cycle in snail: ○ miracidium turns into sporocyst then 1-2 generations of redia before producing cercariae ○ cercariae will leave (5-6 wks at night) ◆ attach itself to aquatic plants (2nd IH) to become metacercariae (Ipomea obscura, Nasturtium of cinale) Fasciola hepatica large, broad, at body suckers: small and close to each other testes: highly branched; ovary: above testes uterus: coiled and short fi fl fl fi fl fl  egg: ○ large, ovoidal and operculated ○ yellowish to browning in color Fasciola gigantica less developed shoulders shorter cephalic cone intestinal ceca are more branched ovary: longer and numerous testes: farther from posterior of the body egg: same w F. hepatica pathogenesis human fascioliasis ○ acute stage ◆ asymptomatic, dyspepsia, fever, RUQ abdominal pain, sudden onset of fever, hepatomegaly, marked eosinophilia ○ chronic stage ◆ asymptomatic, worm obstruction may stimulate in ammation of biliary epithelium which may cause brosis, atrophy of liver parenchyma and periductal cirrhosis due to heavy infection, obstructure jaundice, hemobilia, biliary cirrhosis, acute pancreatitis ectopic sites of parasite migration ○ lungs, subcutaneous tissue, brain, orbit unusual form of fascioliasis ○ ingestion of raw fasciola-infected liver ○ worm will attach to posterior pharynx ◆ causes hemorrhagic nasopharyngitis and dysphagia ◆ aka halzoun and marrara fi fl diagnosis 1. direct detection of fasciola eggs 2. complete blood count 3. abdominal imaging (ultrasound/ct scan/mri/ercp) 4. biopsy treatment 1. triclabendazole (drug of choice) 2. ntazoxanide Clonorchis sinensis located at bile duct and gallbladder of humans and sh eating mammals mode of transmissions: ○ ingestion of metacercaria present in infected raw or undercooked sh excyst in duodenum young ukes proceed to ampulla of Vater to common bile duct adult worms attach to bile duct mucosa by their suckers ○ embed itself w/o forming a permanent epithelial lining ulcer eggs move to intestine together w the bile then wait to be excreted out of body miracidium ○ hatch after eggs is ingested by 1st IH (snail) inside snail ○ miracidium turns into sporocyst then into redia; redia will produce cercaria then release to water cercaria ○ attach to epithelium of 2nd IH (freshwater sh) upon contact thru suckers ○ under sh scale or in muscle, encyst to become metacercaria fi fl fi fi  presence of transparent tegument vitellaria: at level of uterus testes: 2 large highly branched structures at posterior half of body egg: ○ yellowish brown and ovoid ○ 26-30um x 15-17um ○ w small protuberance at abopercular end pathogenesis phases: ○ desquamation of epithelial cells ○ hyperplasia and desquamation of epithelial cells ○ hyperplasia desquamation of epithelial cells and adenomatous tissue formation ○ marked proliferation of periductal connective tisse w scattered abortive acini of epithelial cells, and brosis of biliary duct's wall light infection: ○ asymptomatic ○ nonspeci c clinical signs ◆ diarrhea ◆ abdominal pain moderate infection: ○ fever, diarrhea, inappetence, rash, edema, night blindness, swollen abdomen, hepatomegaly heavy infection: ○ acute pain in RUQ of digestive system chronic stages: ○ liver malfunction fi fi  more severe late complications: ○ calculi ○ acute suppurative cholangitis ○ recurrent pyogenic cholangitis ○ cholecystitis ○ hepatitis ○ pancreatitis diagnosis: 1. microscopic identi cation of egg in stool 2. abdominal imaging treatment: 1. albendazole 2. praziquantel LUNG FLUKE Paragonimus spp. paragonimus westermani ○ asia and oceania ○ widely prevalent adult stage ○ 7.5-12mm. x 4-6mm ○ reddish brown ○ tegument - covered in scalelike spines ○ oral and ventral suckers are same size ○ testes - lobated ○ ovaries - lobated; found below ventral suckers to the left ○ egs - ovoid, w operculum, 80-118um x 48-60um fi  adult worms reside in lungs, encapsulated in pairs by granuloma eggs are trapped by surrounding tissues (can't leave lungs) ○ if escaped, thru air passages; move up and out via ciliary epithilum ○ in pharynx, swallowed and packed thru alimentary canal then out of feces ○ 16 days to several weeks in water before developing into miracidia miracidia ○ needs freshwater snail IH ○ will form sporocysts then redia then cercaria inside snail cercaria ○ enter second IH (mountain crab) ○ turn into metacercariae DH eats mountain crab ○ worms excyst in duodenum ○ juveniles penetrate intestine and embed in abdominal wall ○ reenter coelom and penetrate diaphgram and pleurs ○ penetrate lung and form cyst ○ 8-12 weeks pathogenesis larvae migrate for 1 week adult worms induce in ammatory granulomatous response in lungs generating brous cyst that contains: ○ purulent bloody effusion which eggs are passed unto environment via expectoration ○ eggs released by ukes in spulum which may be swallowed fl fl signs & symptoms asymptomatic (early signs) chronic cough hemoptysis chest pain dysnea low grade fever fatigue generalized myalgia chronic bronchiectasis pleural brosis manifestations cutaneous paragonimiasis cerebral paragonimiasis (most severe) ○ migrates from pleural to cranial cavity via soft tissues along internal jugular veins BLOOD FLUKE Schistosoma spp. schistosoma japonicum ○ embryonated egg from DH's stool will hatch into free swimming miracidia in 2-4 hrs in water ○ miracidia infects snail IH and develop sporocysts (Oncomelania hupensis quadrasi) ○ sporocysts will reproduce asexually = free-swimming cercariae (60-70 days) ○ cercariae will penetrate DH's skin when they come in contact to infested fresh water: ◆ lose tails ◆ transform to schistosomula ◆ enter super cial lymphatic vessels or subcutaneous veins ◆ enter lungs fi fi  ○ schistosomules differentiate into male and female ◆ female larger than male ◇ occupy gynecophoric canal of male ◇ deposit 500-2k immature eggs/day in branches of portal vein ○ eggs will mature and embryonate (10-12 days) ◆ deposited in mucosal or submucosal terminal veins or capillaries ◆ escape thru ulcerations to intestinal lumen ◆ excreted thru feces ◆ will hatch only in clean fresh water w suf cient oxygen egg ○ ovoid, round or pear-shaped ○ pale yellow ○ 46-110um x 37-90um ○ thin shelled where residual tissue or RBC are found ○ cured hook or spine on one end miracidium ○ morphological features ◆ apical papilla ◆ epidermal plates w/ cilia ◆ primitive gut fi  ◆ pair of cephalic unicellular penetration glands ◆ 2 pairs of ame cells ◆ germinal cells ○ phototactic (active swimmers) sporocyst ○ miracidium develops into sporocyst few days after the miracidium penetrates into soft parts of the snail and loses their cilia ○ daughter sporocysts are formed on eighth day from dev't of rst gen ◆ migrate thru loose connective tissue to reach liver cercaria ○ emerge from sporocyst, leave snail into fresh water ○ w/ body and forked tail adult uke ○ large sucker found at anterior end ○ ventral sucker; gonophore posterior to ventral sucker ○ male ◆ w gynecophoric canal to hold female ◆ testes (one row above ventral sucker) ○ female ◆ ovary (single, pyramidal shape in midline) pathogenesis ○ swimmer's itch ◆ cercarial penetration of skin w dermatitis w/ pruritus ◆ self-limiting schistosomule migration ○ snail fever or katayama fever/syndrome ◆ easy fatigability, respiratory symptoms, arthalgia, myalgia, eosinophilia, fever, malaise, hepatosplenomegaly, hepatic dysfunction, death fl fl  migration thru pulmonary circulation ○ wheezing and coughing abberant migration ○ occlude circulation in brain and spinal cord ◆ seizure, paresthesia, transient (resolves in 24 hrs) ischemic attack, stroke chronic schitosomiasis ○ prolonged infection (up to 10 yrs) ○ liver cirrhosis ○ kidney damage ○ urinary bladder damage ○ hepatosplenomegaly ○ ascites 3 stages of clinical course of schistosomiasis infection ○ incubation ○ period of early egg deposition and extrusion ○ period of tissue proliferation diagnosis ○ examination of stool and/or urine for ova ◆ must take at least 3 samples in different days ○ review history of travel or residency history ○ serological test for antischistosomal antibody ◆ collected atleast 6 to 8 weeks after injection treatment ○ praziquantel (most effective against adult worm) ◆ drug of choice ◆ for travelers, treatment should be at least 6-8 wks after last exposure ◆ a single course of treatment is usually curative ◆ repeat treatment may be needed after 2-4 wks Tapeworms Phylum Nemathelminthes (Nematoda) general characteristics ○ elongated, cylindrical worms, frequently attenuated at both ends ○ possess stiff cuticle which may be smooth or may be extended to form a variety of structures (anterior and posterior ends) ○ sexes are separate, male frequency being considerably smaller than female and possess copulatory structures (spicule or bursa) ○ complete digestive tract ○ free living ○ IH are necessary for larval development of some forms ○ intestinal and tissue-inhabiting species in humans ○ two classes based on chemoreceptors: ◆ phasmidia - posses caudal chemoreceptors (phasmids) ◆ aphasmidia - lacks caudal chemoreceptors ○ some possess sensory organs called amphids ○ longitudinally oriented muscles important for locomotion ○ very large: ◆ females: 20-35 cm ◆ males: 15-30 cm ○ A. lumbricoides is primary species involved in human infections globally Ascaris Lumbricoides most common intestinal nematodes aka giant roundworm (most frequent in tropics) 70% of 1 billion individuals infected are from Asia soil-transmitted helminth - means that soil plays a major role in development and transmissio; diseases of poverty epidemiology: ○ 807 mil - 1.2 billion people are infected ○ account for major burden of parasitic disease worldwide  ○ eggs from parasite are passed in human feces ○ eggs survive best in warm, humid areas and must grow in soil before they infect others ○ most cases occur in tropical and subtropical areas ○ Ascaris suum is found wherever pigs are found mode of transmission: ○ ingestion - embryonated egg/ova (Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularis) ○ skin penetration (Strongyloides stercoralis, hookworms) ○ inhalation (Enterobius vermicularis) ○ transmammmary (S. stercoralis, Ancylostoma duodenale) ○ vectors (Filarial worms) life cycle (direct) ○ egg -> larva -> adult ○ eggs vary in size ○ larve: ◆ rhabditiform - stage that hatches from egg larva undergoes several molts until it reaches third stage larva ( lariform; infective form) ○ infective stage: embryonated egg (2-3 wks. in favorable condition) ○ diagnostic stages: ova/egg in stool, adult worm ○ MOT: mature worms start laying eggs in intestinal tract after ingestion ○ life span: dies in abt a year ○ nal host: man ○ adult worms appear creamy-white to pink in color ○ female parasite is highly proli c; laying 2 mil eggs daily ○ larvae hatch from ingested eggs in lumen of small parasite, penetrate into tissue by way of lymph and blood systems and eventually lungs ◆ in lungs, larvae break out of pulmonary capillaries into air sacs, ascends into throat and descend to small intestine fi fi fi  ○ adult parasite lives in lumen of small intestine feeding on semi digested content of gut pathology: ○ varying degrees: ◆ tissue reaction to invading larvae ◆ intestinal irritation to adult ◆ other complications due to extraintestinal migration pathogenesis: ○ bowel obstruction w fever and malaise ○ vomiting ○ pneumonitis during larva migration to lungs ○ intestinal perforation ○ occlusion of appendix ○ lactose maldigestion or intolerance ○ eosinophilia during period of tissue migration ○ increased lgG and lgE ○ ectopic migration to extraintestinal sites clinical manifestatons: ○ asymptomatic ○ abdominal discomfort ○ gut obstruction ○ impair growth (children) ○ cough diagnostic tests: ○ direct fecal smear - abt 2mg feces are emulsi ed in a drop of NSS on a glass slide ○ kato technique or cellophane thick smear - purely quantitative method; recommended for mass examination ○ kato-katz - used to quantify no. of eggs found in a measured fecal sample; used to determine intensity of infection ○ concentration techniques, radiography and cholangiograms fi  treatment and prevention ○ drug of choice: albendazole and mebendazole ○ treatment for bowel obstruction: intravenous hydration, nasogastric suctioning, electrolyte monitoring and laparotomy  Capillaria philippinensis biology ○ tiny nematode residing in small intestine ○ male worms length: 1.5 - 3.9 mm ○ female worms length: 2.3 - 5.3 mm ○ male spicule is 230 - 300 um long and has unspined sheath ○ have thin lamentous anterior end and slightly thicker and shorter posterior end ○ esophagus has rows of secretory cells (stichocytes) ○ anus is subterminal and vulva in females is located at junction of anterior end and middle thirds eggs ○ peanut-shaped w striated shells and attemed bipolar plug ○ measure to 36 to 45 um by 20 um life cycle ○ eggs are passed in feces and embryonate in soil or water ○ must reach wayer in order to be ingested by small species of freshwater or brackish water sh ○ eggs hatch in intestine of sh and grow into infective larvae ○ when eaten uncooked: larvae escape from sh intestine and develop into adult worm in human intestines fi fi fi fi fl  ptahogenesis & clinical manifestations ○ abdominal pains, gurgiling stomach and diarrhea ○ after a few wks, there is a noticeable weight loss, malaise, anorexia, vomiting and edema ○ laboratory ndings show severe protein-losing enteropathy, malabsorption of fats and sugar, decreased excretion of xylose, low electrolyte levels (esp. potassium) and high levels of lgE treatment ○ antidiarrheal and anthelminthic drugs should be given ○ anthelminthics: ◆ mebendazole ◆ albendazole ○ electrolyte replacement and high rpotein and high protein diet fi Tissue-dwelling Nematodes Dracunulus medinensis (Guinea worm) transmission ○ only helminthic parasite transmitted solely thru water ○ usually occurs during drought where everyone is forced to drink from same stagnant water supplies or pay for well ○ three conditions to be met before D. medinensis can complete its life cycle ◆ skin of infected individual must come in contact with water ◆ water must contain appropriate species of microcrustacean (copepod) ◆ water must be used for drinking ○ believed parasites feed on blood due to gut often being lled with dark brown gut material life cycle diagnosis ○ made from local blister, worm or larvae ○ outline of worm under skin ○ s treatment ○ drug therapy: metronidazole ○ anti-in ammatory to help extraction of adult ○ treatment includes extraction of adult guinea worm by rolling it a few centimeters per fl  day usually takes wks or months depending on how long worm is ○ exposing area to cold water helps remove worm faster ○ preferably by multiple surgical incisions under local anesthesia ○ infection does not make a person immune Trichinella spiralis (Muscle/Trichina worm) parasitic to carnivorous mammals (rats and in swine fed uncooked garbage) humans get infected from uncooked prok nal host: swine dead end host: man habitat: small intestines (adult form) striated muscles (larvae) biology ○ whitish in color and measures 1.5 x 3.5 mm by 0.04 to 0.06 mm ○ male: 1.5 mm by 0.04 mm; single testis located near posterior end of body and is joined in mid-body by genital tube which extends back to cloaca ○ female: measures fi