Parasitology Quiz on Nematodes and Filariasis

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Questions and Answers

What is the primary way pigs become infected with larvae?

Pigs become infected by eating infected flesh from other pigs or ingestion of infected dead.

List two major clinical symptoms associated with intestinal invasion by adult worms.

Abdominal pain and nausea.

What factors determine the manifestations of larval encystment?

Manifestations depend upon the organs affected and the number of larvae present.

What laboratory technique can be used for the immunodiagnosis of the condition?

The Intradermal test (Bachman test) is one technique used. Signup and view all the answers

What is one method to prevent infection through food?

Thorough cooking of pork is one preventive method. Signup and view all the answers

Name two supportive treatment measures for infected individuals.

Rest and fluid intake. Signup and view all the answers

What is the significance of eosinophilic leucocytosis in diagnosis?

Eosinophilic leucocytosis indicates an acute stage of infection. Signup and view all the answers

Identify two drugs used in the treatment of this condition.

Thiabendazole and Mebendazole. Signup and view all the answers

What is the typical cause of elephantiasis related to Wuchereria bancrofti?

Elephantiasis related to Wuchereria bancrofti is caused by an immune response to the parasites, leading to lymphoedema. Signup and view all the answers

What are the general preventive measures for controlling W.bancrofti?

Preventive measures include controlling mosquitoes, avoiding bites, treating patients, and health education. Signup and view all the answers

Identify the main habitat of Loa loa in the human body.

Loa loa primarily inhabits connective tissues under the skin, mesentry, parietal peritoneum, and subconjunctival tissue of the eye. Signup and view all the answers

Describe the typical morphology of adult Loa loa worms.

Adult Loa loa worms are cylindrical and transparent in appearance. Signup and view all the answers

What role do horse flies play in the transmission of Loa loa?

Horse flies, specifically those in the genus Chrysops, are responsible for the transmission of Loa loa by biting and transferring larvae. Signup and view all the answers

What is a common characteristic of the microfilariae of Loa loa?

Microfilariae of Loa loa exhibit several curves and kinks in their body, with a sheath that stains best with haematoxylin. Signup and view all the answers

Explain the clinical manifestation of Loiasis.

Loiasis is often asymptomatic, which can complicate diagnosis and treatment efforts. Signup and view all the answers

What treatment is typically recommended for Wuchereria bancrofti infections?

Diethyl carbamazine (DEC) is the standard treatment for infections caused by Wuchereria bancrofti. Signup and view all the answers

What are the three primary filarial worms responsible for most morbidity, and what diseases do they cause?

The three primary filarial worms are W. bancrofti and B. malayi, which cause lymphatic filariasis, and O. volvulus, which causes onchocerciasis. Signup and view all the answers

Describe the importance of timing when collecting blood for diagnosing filarial infections.

Blood should be collected at specific times due to the periodicity of microfilaria presence, with higher concentrations typically seen at night for nocturnal species. Signup and view all the answers

What morphological features are considered when identifying microfilaria in blood samples?

Key morphological features include size, sheath presence, curvature, and arrangement of nuclei. Signup and view all the answers

What is the significance of the adult filarial worms' size and habitat?

Adult filarial worms measure between 2 cm and 120 cm and reside in body cavities, lymphatics, and subcutaneous tissues, facilitating their role in transmission and pathology. Signup and view all the answers

What is 'periodicity' in the context of filarial worms, and how does it relate to their vectors?

Periodicity refers to the timing of microfilaria presence in the blood, correlating with the peak biting times of their insect vectors. Signup and view all the answers

Explain the role of microfilaria in the life cycle of filarial worms.

Microfilaria are the immatures first stage larvae that live in blood or dermis and are necessary for transmission to the intermediate host, typically an insect or crustacean. Signup and view all the answers

What causes the diurnal or nocturnal periodicity observed in microfilaria of pathogenic filarial worms?

Diurnal or nocturnal periodicity is determined by the life cycle of the worms and the feeding habits of their insect vectors, influencing when microfilaria are most abundant in blood. Signup and view all the answers

What characteristics define microfilaria, and how can they be observed?

Microfilaria are motile, transparent, colorless, measuring 150-350 µm long, and can be sheathed or unsheathed; they can be observed using fixed stained preparations. Signup and view all the answers

What are the primary geographic regions associated with Wuchereria bancrofti?

Wuchereria bancrofti is primarily distributed in tropical and subtropical countries. Signup and view all the answers

Describe the morphology of adult female Wuchereria bancrofti.

The adult female Wuchereria bancrofti measures about 8 cm in length, has two sets of genitalia, and its vulva opens near the posterior end. Signup and view all the answers

What role do mosquitoes play in the transmission of Wuchereria bancrofti?

Mosquitoes serve as intermediate hosts, transmitting infective larvae to humans through their bite. Signup and view all the answers

What are the key stages of microfilariae development in humans?

After entering the lymphatic system, microfilariae undergo further molts to develop into adult male and female worms. Signup and view all the answers

How long after infection can microfilariae from Wuchereria bancrofti typically be found in the blood?

Microfilariae from Wuchereria bancrofti can be found in the blood about nine months after infection. Signup and view all the answers

What is the morphology of microfilariae of Wuchereria bancrofti?

Microfilariae are approximately 250 x 8 μm and have graceful curves with a column of nuclei separated by free areas. Signup and view all the answers

What is the size range of infective larvae of Wuchereria bancrofti?

Infective larvae measure between 1500 – 2000 x 20 μm. Signup and view all the answers

How do microfilariae enter the mosquito's hemocoel during the lifecycle?

Microfilariae penetrate the mosquito's stomach wall and migrate to the hemocoel after being ingested during a blood meal. Signup and view all the answers

What are the characteristics of Calabar swellings?

Calabar swellings are itchy, red, nonpitting swollen areas in the skin, typically measuring 2-10 cm in diameter, and can be painful or painless. Signup and view all the answers

How can Loa loa microfilariae be identified in laboratory diagnostics?

Loa loa microfilariae can be identified in stained blood films taken during the daytime and occasionally in joint fluid. Signup and view all the answers

What is the primary cause of onchocerciasis, and where is it commonly found?

Onchocerciasis is caused by the filarial worm Onchocerca volvulus and is commonly found near fast-running rivers in West and Central Africa. Signup and view all the answers

What is the significance of Onchocerciasis in global health?

Onchocerciasis, also known as river blindness, is the world's second leading infectious cause of blindness, affecting approximately 270,000 individuals globally. Signup and view all the answers

Describe the habitat of adult Onchocerca volvulus.

Adult Onchocerca volvulus inhabit subcutaneous nodules and the skin, where they can live for approximately 8 to 10 years. Signup and view all the answers

What are the differences in morphology between Loa loa and Mansonella perstans?

Loa loa has a sheath, a relatively dense nuclear column, and a frequently coiled tail, while Mansonella perstans is smaller, has no sheath, and a blunt tail. Signup and view all the answers

What is the typical size range of Onchocerca volvulus microfilariae?

Onchocerca volvulus microfilariae typically measure between 220 to 360 µm in length and 5 to 9 µm in width. Signup and view all the answers

Where do the infective larvae of Onchocerca volvulus develop?

Infective larvae of Onchocerca volvulus develop in the gut, mouthparts, and muscles of blackflies. Signup and view all the answers

What is the primary vector responsible for the transmission of Onchocerca volvulus?

The primary vector is the blackfly, specifically Simulium species. Signup and view all the answers

Describe the life cycle of Onchocerca volvulus from the moment it is transmitted to humans.

Infected blackflies introduce L3 larvae onto the skin, which then penetrate the bite wound and develop into adult filariae in the subcutaneous tissues. Signup and view all the answers

How long do female Onchocerca volvulus worms typically produce microfilariae (Mf)?

Female worms produce microfilariae for approximately 9 years. Signup and view all the answers

What are the two major types of clinical manifestations of onchocerciasis?

The two major types are acute onchocerciasis and chronic onchocerciasis. Signup and view all the answers

What distinctive diagnostic method is used to detect the presence of microfilariae in suspected onchocerciasis cases?

Microfilariae can be detected through skin snips or biopsies. Signup and view all the answers

What is the primary mode of preventing onchocerciasis transmission?

Prevention focuses on the destruction of Simulium blackflies and avoiding their bites. Signup and view all the answers

What is the function of ivermectin in the treatment of onchocerciasis?

Ivermectin causes paralysis of the worms and reduces the microfilarial load. Signup and view all the answers

What is the surgical procedure called that removes adult worms from nodules?

The surgical procedure is called nodulectomy. Signup and view all the answers

Study Notes

Blood and Tissue Nematodes

Blood and tissue nematodes live in human tissues, including the lymphatic system, subcutaneous tissues, or muscles.
They are thread-like worms.
They require two hosts to complete their life cycle.
Females are viviparous, meaning larvae hatch inside the uterus.
The female produces first-stage larvae (L1).
The immature L1 stage larva is called Microfilariae.
L1 larvae require blood-sucking insects to develop into the infective form (L3).
There is no reproduction in the insect vector, only development.
Tissue nematodes can be classified based on their habitat in the body, clinical manifestations, and morphology.

Three Families/Groups of Tissue Nematodes

FAMILY FILARIDAE (Filarial worm): Common/pathogenic filaria
- Wuchereria bancrofti
- Brugia malayi
- Brugia timori
- Loa loa
- Onchocerca volvulus
Less/non-pathogenic Filaria:
- Mansonella perstans
- Mansonella streptocerca
- Mansonella ozardi
FAMILY TRICHINELOIDAE:
- Trichinella spp
FAMILY DRACUNCULIDAE (Guinea worm):
- Dracunculus medinensis

Animal Tissue Nematodes

Dirofilaria spp
Angiostrongylus cantonensis
Gnathostoma spinigerum

Family Filaridae (Filarial Worm)

Filariae live as adults in various human tissues.
Agents of lymphatic filariasis (LF) reside in lymphatic vessels and lymph nodes
Onchocerca volvulus, Loa loa, M. Ozzardi and M. Streptocerca reside in subcutaneous tissues
M. Streptocerca also reside in the dermis.
M. Perstans resides in body cavities and surrounding tissues.

Morbidity of Filarial Worms

W. bancrofti and B. malayi cause lymphatic filariasis.
O. volvulus causes onchocerciasis (river blindness).

Diagnosis of Filarial Worms

Morphology (size, presence of sheath, curvature, arrangement of nuclei, presence of nuclei at tail tip) is used in diagnosis.
Factors to consider when collecting blood include the correct time of collection and the concentration technique.

Filarial Worm Morphology (FAMILY FILARIDAE)

Adults are long, thread-like worms, measuring 2 cm to 120 cm (4-10 µm wide).
Microfilariae are immature larvae, measuring 150-350 µm, transparent and colorless, with rounded or pointed tails.
They are motile and live in blood or dermis.
Their internal structure is visible with fixed, stained preparations.
Some microfilariae are sheathed, others are not.

Periodicity of Microfilariae

Microfilariae of pathogenic filarial worms (causing lymphatic filariasis and loasis) manifest periodicity.
Microfilariae are commonly found in higher numbers during specific hours of the day or night reflecting peak biting times of their insect vectors.
- Nocturnal periodicity: high mf count in blood during night.
- Diurnal periodicity: high mf count in blood during day.

Filarial Worms: Periodicity, Vector, and Reservoir

O. volvulus (river blindness): non-periodic, black fly, human
W. bancrofti (lymphatic filariasis): periodic (22 - 04hr), Culex, Anopheles, Aedes, human
B. malayi (lymphatic filariasis): periodic (22- 04hr), Anopheles, human; Reservoir = human, monkey, cat.
B. timori(lymphatic filariasis): periodic (20 - 22hr), Anopheles, human; Reservoir = Human L. Loa (Eye worm): periodic (D), deer fly, man, monkeys

Filarial Worm Diseases

Filarial worms cause lymphatic filariasis (elephantiasis), loiasis, and onchocerciasis (river blindness).

Lymphatic Filariasis

Caused by Wuchereria bancrofti and Brugia malayi (and Brugia timori).
These worms reside in the lymphatic system and live for several years, producing millions of minute larvae.
Affected areas include lower extremities, upper extremities, male genitalia.
The disease can cause disfigurement, leading to stigma, anxiety, ostracization, and psychological trauma, and also hinders mobility, travel, educational and employment opportunities, and marriage prospects.
Epidemiology of lymphatic filariasis includes prevalence in 83 countries with 1.2 billion at risk.
120 million are infected, and ~2/3 of them live in India or Africa.

Onchocerciasis

Caused by Onchocerca volvulus.
Common in tropical and subtropical areas.
The most common way is distributed along fast moving rivers in forests and savanna of west and central Africa; also occurs in the Yemen, Arab Republic, and South America.
Subcutaneous nodules and in the skin.
Adult worms can live in nodules for ~8-10 years. Microfilarial.
Infective larvae in gut, mouth parts, and muscles of blackflies.

Onchocerca volvulus: Morphology

Microfilariae measure 220-360 µm by 5-9 µm.
There is no sheath.
Head end is slightly enlarged.
Anterior nuclei are positioned side to side. There are no nuclei in the tail end.
Adult females measure 33-50cm long, 270-400µm, whereas males are 19-42 mm long, 130 - 210µm.

Onchocerciasis: Transmission, Life Cycle, and Clinical Features

Transmission is by blackfly bite. (Simulium species).
Lifecycle includes the blackfly ingesting microfilariae during a blood meal, larvae developing into L3, L3 migrating to the blackfly's proboscis, and infection occurring when a blackfly bites a human.
Adult worms commonly reside in nodules.
Female worms produce microfilaria for nine years. Microfilaria live for ~ two years. They are typically found in skin and lymphatic tissues.
Acute onchocerciasis present with itchy, erythematous, or papular rashes and skin thickening. Chronic features include elephant or lizard skin, and harlequin-like coloration.
Clinical manifestations include onchocercomata: The inflammatory lesions in the skin include nodules surrounded by concentric bands of fibrous tissue of the upper part of the body (and pelvic form).
Laboratory diagnosis is done using skin snips, and urine, blood, or other body fluids that are examined under a microscope for microfilariae.

Trichinellosis

Caused by Trichinella spiralis, a tissue nematode.
Distribution is in temperate regions where pork is part of the diet.
Hosts include pigs and rats.
Larvae are encysted in muscles.
Adults live in the small intestine of humans and animals (pigs).
Infective larvae develop inside the cyst, grow to 0.1 to 1 mm in length in ~ two weeks, and lies along the longitudinal axis of muscles.

Trichinellosis: Morphology and Transmission

Adults have an attenuated anterior end, cellular esophagus, and end in an anus or cloaca. Males measure 1.5mm long with a posterior end curved ventrally and two caudal papillae. Females measure 3.5 mm long and have a bluntly rounded posterior end with a single set of genitalia and vulva at the anterior-body junction.
Larval cysts form within infected muscle tissues (striated muscle); they are coiled and can grow from 0.1 mm to 1 mm.
Transmission occurs via consumption of raw or undercooked infected pork.

Trichinellosis: Life Cycle and Pathogenicity

Animals (pigs or rodents) become infected by eating infected flesh or ingestion of infected dead animals (cannibalism).
Adult worms invade the intestinal wall. Larvae migrate to the circulation and are distributed to skeletal muscle cells via blood vessels.
Cysts encyst in skeletal muscle.
Larvae release from cysts and migrate to various parts of the body.
Cyst localization and larval loads affect clinical symptoms.
Symptoms associated with the intestinal invasion by adult worms include abdominal pain, nausea, vomiting, diarrhea, and colic.
Symptoms of larval migration include oedema (chiefly orbital), muscle pain and tenderness, headache, fever, rash, dyspnoea, general weakness, and death in severe cases due to exhaustion, heart failure, myocarditis, or pneumonia.

Dracontiasis (Dracunculus medinensis)

Also known as Guinea worm disease.
Caused by Dracunculus medinensis.
Most common in areas of limited water supply where acquiring water involves physically entering water sources ("walk-in wells" or water holes). Distribution includes parts of Africa, India, and the Nile Valley.
Adult worms reside in subcutaneous tissues of humans.
Adult worms are threadlike, elongated, and have a cylindrical esophagus. Males measure ~3cm, have a coiled posterior end, and have 2 unequal spicules. Females are 30-100cm long and anterior end is swollen.

Dracontiasis: Life Cycle and Pathogenicity

Humans are infected by drinking water containing copepod (crustacean) intermediate hosts.
Larvae penetrate the small intestine and migrate to subcutaneous tissues via lymphatics.
Fertilized females migrate to the skin, reach maturity, and produce juveniles. The cephalic end presses on the skin causing a papule that develops into a blister and ulcer.
Larvae are discharged from the ulcer when the water comes in contact with the ulcer.
Symptoms include a blister, which may cause pain, erythema, and tenderness, and may become infected, causing cellulitis and induration.
Diagnosis is typically made when the anterior end of a female worm is observed within a ruptured blister; Lab tests are limited due to larvae usually washing into water.

Dracontiasis: Prevention and Treatment

Prevention involves avoiding water sources where copepods might present. If necessary, water can be boiled or filtered using tightly woven cloth.
No medication exists to end or prevent the infection though individuals may consider surgical intervention to remove the worm.

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Test your knowledge on nematodes and filarial infections with this quiz. It covers infection routes, symptoms, diagnostic techniques, and treatment options related to various parasitic conditions including those caused by Wuchereria bancrofti and Loa loa. Perfect for students and professionals in parasitology or medical fields.