2Hookworms of medical importance & Trichinella spiralis Filarial worms W.bancroftii Doç.Dr.Hrisi BAHAR
3Ancylostoma and Necator (Hookworms) Causative agents of ancylostomosis and necatorosis (hookworm infection)Ancylostoma duodenaleNecator americanusare common parasites of the human small intestine, causing enteritis and anemia.Infection is mainly by the percutaneous route.
4Ancylostoma and Necator (Hookworms) Occurrence.●Human hookworm infections are mostfrequent in the subtropics and tropicsarea in southern Europe, Africa, Asia,SouthernUS, Central and South America.● In central Europe, hookworm infectionsare seen in travelers returning from thetropics or in guest workers from southerncountries.
5Ancylostoma and Necator (Hookworms) MorphologyThe hookwormsthatparasitize humansare 0.7–1.8 cm longwith the anteriorend bent dorsally ina hooklike shape
6Ancylostoma and Necator (Hookworms) The entranceto the large buccal capsule is armed with toothlike structuresAncylostoma duodenale
7Ancylostoma and Necator (Hookworms) The entranceto the large buccal capsule is armed withcutting platesNecator americanusNecator americanus
9Ancylostoma and Necator (Hookworms) ● The thin-shelled, oval eggs (about 60µm long)containing only a small number of blastomeres are shed with feces. In one to two days the first-stage larvae leave the egg molt twice, and develop into infective third-stage larvae.
10Ancylostoma and Necator (Hookworms) ● Since the shed second-stage cuticle is not entirely removed, the third-stage larva is covered by a special sheath.● Larvae in this stage are sensitive to dryness.
11Ancylostoma and Necator (Hookworms In moist soil or water they remain viable for about one month.Higher temperatures (optimum:20–30 8C) and sufficient moisture is favor for the development of the parasite stages outside of a host.
12Life Cycles of Hookworms ● Humans are infected mainly by the percutaneous route.● Factors favoring infection include working in rice paddies, walking barefoot on contaminated soil.
13Life Cycles of Hookworms 1-In favorable conditions of moisture, temperature, and oxygen, eggs develop in the soil and hatch when they reach maturity.2-They release a rhabditiform larva which feeds for a short time and molts twice before becoming an infective filariform larva.
14Life Cycles of Hookworms Filariform larva enters the host either by being swallowed or through hair follicles.
15Life Cycles of Hookworms 3-While penetrating the skin, the larvae shed their sheaths and migrate into lymphatic and blood vessels.2-Once in the bloodstream, they migrate viathe right ventricle of the heart and by trachealmigration into the small intestine, where theydevelop to sexual maturity.
18Life Cycles of Hookworms ● Following oral infection, immediate development in the intestine is probably possible , without the otherwise necessary migration through various organs.● The parasites can survive in the human gut for one to 15 years.
19Ancylostoma and Necator (Hookworms Clinical manifestation● Hookworms are bloodsuckers. The buccal capsule damages the mucosa and induces inflammatory reactions.● The intestinal tissue damage results in diarrhea with bloody admixtures, steatorrhea, loss of appetite, nausea, flatulence, and abdominal pains.
20Ancylostoma and Necator (Hookworms General symptoms1-Iron deficiency anemia due to constant blood loss2-Edemas caused by albumin losses3-Weight loss due to reduced food uptake and malabsorption.4-Blood eosinophilia is often present.Mild infections cause little of clinical note.
21Ancylostoma and Necator (Hookworms Diagnosis.●Diagnosis relies on finding of eggs in stoolsamples.● The eggs are thin-shelled and oval● When fresh they contain only two to eightblastomeres● The eggs in older stool samples have alreadydeveloped a larger number of blastomeres
23Ancylostoma and Necator (Hookworms Therapy and controlDrugs effective against hookworms arepyrantel, mebendazole,and albendazole.Practicable preventive and control measuresinclude mass chemotherapy of the populationin endemic regions, reduction of disseminationof hookworm eggs byadequate disposal of fecal matterand reduction of percutaneous infection byuse of properly protectiv footwear
24Nematodal Infections of Tissues and the Vascular System Filarial nematodesTrichinella
25FilariaeThe nematode genera of the superfamily Filarioidea will be here under the collective term filariae, and the diseases they cause are designated as Filarioses.In the life cycle of filariae infecting humans,insects (mosquitoes, blackflies, flies etc.)function as intermediate hosts and vectors.Filarioses are endemic in subtropical andtropical regions; in other regions they areobserved as occasional imported cases.
26Filariae The most important filariosis is onchocercosis, the causative agents is Onchocerca volvulus,istransmitted by blackflies.Microfilariae of this species can cause severe skinlesions and eye damage, even blindness.Diagnosis of onchocercosis is based on clinicalsymptoms,detection of microfilariae in the skinand eyes, as well as on serum antibody detection.
27Filariae Other forms of filarioses include lymphatic filariosis .The causativeagent is Wuchereria bancrofti, Brugiaspecies and Loaosis that thecausative agent is Loa loa. Dirofilariaspecies from animals can cause lungand skin lesions in humans
29Filariae surrounded by an extended eggshell ● Filariae are threadlike nematodes.● The length of the adult stages of the species that infect humans varies between 2–50 cm whereby the females are larger than the males.● The females release embryonated eggs or larvae called microfilariae.● The eggs are about 0.2–0.3 mm long,surrounded by an extended eggshell● They can be detected in the skin or in blood
30Filariae● Based on the periodic appearance of microfilariae in peripheral blood, periodic filaria species are differentiated from the nonperiodic ones showing continuous presence.● The periodic species produce maximum microfilaria densities either at night (nocturnal periodic) or during the day (diurnal periodic).● Different insect species, active during the day or night, function as intermediate hosts accordingly to match these changing levels of microfilaremia.
31Ingestion of microfilaria with a blood meal Life Cycle of FilariaeInsect:Ingestion of microfilaria with a blood mealdevelopment in thoracic musculature with two moltings to become infective larvamigration to mouth parts and tranmission into skin of a new host through puncture wound during thenext blood meal.
32Life Cycle of Filariae Human Migration to definitive localizations and further development with two moremoltings to reach sexual maturity.
34Wuchereria bancrofti Causative agents of lymphatic filariosis About 120 million people in 80 countries suffer from lymphatic filariosis caused by Wuchereria bancroftii or Brugia species(One-third each in India and Africa, the rest in southern Asia, Pacific region,and South America),
35Wuchereria bancrofti Life cycle and epidemiology ●Humans are the only natural final hosts ofW. bancrofti.●The intermediate hosts of W. bancrofti arevarious diurnal or nocturnal mosquitogenera.
36Wuchereria bancrofti ● The development of infective larvae in the insects is only possible at highenvironmental temperatures and humiditylevels;● In Wuchereria bancrofti the process takes about 12 days at 28 ºC.
39Wuchereria bancrofti● Following a primary human infection,the filariae migrate into lymphatic vessels where they develop to sexual maturity.● Microfilariae appear in the blood after seven to eight months.
40Wuchereria bancrofti ● Pathogenesis and clinical manifestations. The initial symptoms can appear as early as1 month , although in most cases the incubationperiod is 5 to 12 months or much longer.Asymptomatic infection,is withmicrofilaremia that can persist for years.
41Wuchereria bancrofti Swelling of lymph nodes, Acute symptomatic infection:Inflammatory and allergic reactions in the lymphatic system caused by filariaeSwelling of lymph nodes,lymphangitis, general malaise, swellings onegs, arms, scrotum, orchitis.
42Wuchereria bancrofti Chronic symptomatic infection Chronic obstructive changes in the lymphatic systemhindrance or blockage of the flow of lymph and dilatation of thelymphatic vessels (“lymphatic varices”)Indurated swellings caused by connective tissue proliferation inlymph nodes, extremities (especially the legs, “elephantiasis”),the scrotum. thickened skin ,lymphuria, when lymph vesselsrupture.This clinical picture develops gradually in indigenous inhabitantsover a period of 10–15 years after the acute phase, in immigrantsusually faster.
43Wuchereria bancrofti Tropical, pulmonary eosinophilia Syndrome with coughing, asthmaticpulmonary symptoms, high-level bloodeosinophilia, lymph node swelling and highconcentrations of serum antibodies(including IgE) to filarial antigens.No microfilariae are detectable in blood, butsometimes in the lymph nodes and lungs.This is an allergic reaction to filarial antigens
46Wuchereria bancrofti1-A diagnosis can be based on clinical symptoms (frequent eosinophilia)2-Finding of microfilariae in blood (sampling at night for nocturnal periodic species).3-Microfilariae of the various species can be differentiated morphologically in stained blood smears and byDNA analysis.
47Wuchereria bancrofti 4-Detection by ultrasonography, particularly in the male scrotal area.5-Detection of serum antibodies (group-specific antibodies, specific IgE and IgG subclasses) and circulating antigens6-The recent development of a specific ELISA and a simple quick test (the ICT filariosis card test ıs usefull for serology.
48Wuchereria bancroftiTherapy. Both albendazole and diethylcarbamazine have been shown to be at least partially effective against adult filarial stages.However, optimal treatment regimens still need to be defined.
49Wuchereria bancrofti ● In 1997, the WHO initiated a program to eradicate lymphatic filariosis.The controlmeasure is mass treatment of populations inendemic areas with microfilaricides.● Concurrent single doses of albendazole witheither ivermectin or diethylcarbamazineare99% effective in removing microfilariae fromthe blood for 1 year after treatment withmeasure of mosquito bites.
50Trichinella Causative agent of trichinellosis ● Humans can acquire an infection with larvae of various Trichinella species by ingesting raw meat (from pigs, wild boars, horses, and other species).● Adult stages develop from the larvae and inhabit the small intestine, where the females produce larvae that migrate through the lymphatics and bloodstream into skeletal musculature, penetrate into muscle cells and encyst.
51Trichinella Occurence Eight Trichinella species and several strains have been described to date basedon typical enzyme patterns, DNAsequences,and biological characteristics.The most widespread and most important species is Trichinella spiralis.
52Trichinella Male Trichinella spiralis are approximately 1–2mm long, the females 2–4mm.The larvae are released following exposure to thedigestive juices,whereupon they invade epithelial cellsin the small intestine.Reaching sexual maturity within a few days after fourmoltings. The males soon die after copulation, thefemales live for about four to six weeks.Each female produces about 200–1500 larvae (eacharound100 lm long), which penetrate into the laminapropria.
53TrichinellaThe larva penetrates into organs and body tissues by lymphogenous and hematogenous migration.Development occurs only in striated muscle cells that they reach five to seven daysThe larvae penetrate into muscle fibers, which are normally not destroyed.
54Trichinella The muscle cell begins to encapsulate the parasite. Encapsulation is completed after four to six weeks.The capsules are about 0.2–0.9mmlong with an oval form resembling alemon.
55TrichinellaThe encapsulated Trichinella remain viable for years in the hostThe developmental cycle is completed when infectious muscle Trichinella are ingested by a new host.