Tissue Nematodes Flashcards
Tissue Nematodes
Trichinella sprialis Dracunculus medinensis Filariasis Loa loa Onchocerciasis
Common name: Trichina worm
Trichinella spiralis
Found in undercooked pork (bear/horse) and game meats worldwide
Trichinella spiralis
Pathogenesis Adults in the intestines: Mild to severe diarrhea Larval migration: High eosinophilia Allergic and toxic reactions May be fatal
Trichinella spiralis
Larval encystment: Primarily in striated muscle
Rheumatoid pain
Toxic reaction
May be fatal: Five larvae per gram of body weight
Fatalities often within 4 to 8 weeks
Caused by: Toxemia, pneumonitis, myocardial failure, or trichinous encephalitis
Trichinella spiralis
Infective third stage larvae encyst in striated muscle
Trichinella spiralis
Non-striated muscle and other tissues do not support development to third stage larvae
Larvae cause local inflammation and tissue damage that have serious pathologic consequences (myocarditis, encephalitis, meningitis)
Trichinella spiralis
Watery diarrhea, vomiting, abdominal discomfort, nausea during enteral phase.
Facial and periorbital edema, fever, weakness, malaise, myalgia, urticarial rash, conjunctivitis and conjunctival and subungual hemorrhages appear during systemic phase (larvae disseminate).
Pts with high infection burden may die of myocarditis, encephalitis, or pneumonia.
Muscle pain and weakness in chronic cases.
Trichinella spiralis
Consider Trichinosis in patients presenting with myositis, eosinophilia 40-50% in a differential, fever, elevated creatine phosphokinase and lactate dehydrogenase
Trichinella spiralis
Size Male: About 1.5 mm Female: 3 to 4 mm Shape: Slender, tapers to larger posterior end Color: Colorless Male has two caudal appendages
Trichinella spiralis
Adults in small intestine mating and depositing larvae (mild phase)
Larvae migrate to striated muscles (severe phase) edema, eosinophilia, myositis, death can occur
Trichinella spiralis
Larvae survive in “nurse cells” for about 6 years.
Diagnosis: history, clinical signs, muscle biopsy
Trichinella spiralis
Common name: Guinea worm
Dracunculus medinensis
Female migration: Severe allergenic reactions
Toxemia: As the female reaches the surface of the body
Gastrointestinal upset
Blisters: Usually on lower extremities
- Severe burning and itching (pruritis)
- Symptoms are relieved when the blister ruptures
Dracunculus medinensis
Surgical removal of the adult worm, “Twist-stick” method
Immersion of affected body part in cool water to coax worm from lesion
No antihelmintic drug is effective
Dracunculus medinensis
Shape: Elongated, cylindrical, rope-like
Color: White
Buccal structures: Small triangular mouth surrounded by a quadrangular sclerotized plate
Dracunculus medinensis
Acquired by ingesting an infected copepod, usually in water.
Larvae penetrate into humans deep connective tissue, mate, then migrate to subcutaneous tissues.
Dracunculus medinensis
Maturity takes about a year.
Gravid female creates an ulcer in the lower limbs and releases larvae upon contact with water.
Diagnosis: clinical signs of muscle pain, ulcer
Dracunculus medinensis
Lymphatic filariasis
Wucheria bancrofti
Burgia malayi
Mainly blood/lymphatic organisms.
Generally transmitted via bites from flies/mosquitoes
Most are tropical diseases
Microfilariae
Once in blood, go to target sites and mature at those locations, causing symptoms
Symptoms include inflammation and swelling due to edema or blockage of vessels
Microfilariae
Habitat: Lymphatic system Intermediate host (vector): Mosquitoes Reservoir host: None Infective form: Filariform larva Mode of infection: Inoculation
Wuchereria bancrofti
Common name: Elephantiasis worm
Pathogenesis: Elephantiasis, fibrosis, thrombi, lymphatic inflammation, granulomatous infiltration
Effective against microfilariae, poor impact on adults which live for 5-7 years.
Doxycycline kills Wolbachia symbionts* and may reduce fecundity and shorten reproductive life span of adults
Wuchereria bancrofti
The most severe cases are referred to as elephantiasis
Wuchereria bancrofti
History is important. Exposure to mosquitoes in endemic areas
Microscopic examination of thick and thin blood smears. Best obtained at night. Nucleopore concentration and other methods (Knott’s Conc.) are helpful
ELISA serology is reportedly available
Wuchereria bancrofti
Common name: Elephantiasis worm
Brugia malayi
Habitat: The lymphatic system Intermediate host (vector): Mosquitoes Reservoir host: None Infective form: Filariform larva Mode of infection: Inoculation
Brugia malayi
Pathogenesis: Elephantiasis, fibrosis, thrombi, lymphatic inflammation, granulomatous infiltration
Brugia malayi
Specimen processing: Giemsa or Hematoxylin/Eosin stains
Specimen of choice: Blood
Periodicity: Nocturnal with some subperiodic strains
Brugia malayi
Adults in lymphatics, microfilariae in blood vessels around the lungs or peripheral areas.
Symptoms: from adult worms, lymphangitis, lymphadenitis, can lead to elephantiasis
Diagnosis: Blood test for microfilariae, sonography, may have serology or PCR
W. bancrofti
B. malayi
(lymphatic filariasis)
Common name: Eyeworm
Loa loa
Pathogenesis: Calabar swelling, urticaria, fever, neurologic symptoms, allergenic responses, irritation and destruction of ocular tissues
Loa loa
Habitat: The subcutaneous and deep connective tissue
Intermediate host (vector): Tabanid fly, Chrysops species
Reservoir host: Monkeys
Infective form: Filariform larva
Mode of infection: Inoculation
Loa loa
Most persons are asymptomatic. Transient Calabar swellings are noted in some
Adult worms may migrate to the conjunctiva – eye worm
Renal complications (hematuria, proteinuria) and encephalitis may be noted after treatment with diethylcarbamazine
Loa loa
Central and W Africa.
Spread by the bite of the Chrysops spp flies (deer or mango flies)
Adults in subcutaneous tissue (eye)
Loa loa
AKA the African Eye Worm
Loa loa
Symptoms: Calabar swelling (migratory edema), high eosinophilia, worm in eye
Diagnosis: Calabar swelling, microfilariae in blood (drawn during the day)
No Wolbachia symbiont
Loa loa
Symptoms: Calabar swelling (migratory edema), high eosinophilia, worm in eye
Diagnosis: Calabar swelling, microfilariae in blood (drawn during the day)
No Wolbachia symbiont
Loa loa
Habitat: Cutaneous and subcutaneous tissues
Intermediate host (vector): Black flies (buffalo gnats), Simulium species
Reservoir host: None
Infective form: Filariform larva
Mode of infection: Inoculation
Onchocerca volvulus
Adults live in subcutaneous nodules
Pathology is the host’s inflammatory response to the microfilariae
In the eye, microfilariae initially elicit punctate keratitis which can progress to a sclerosing keratitis and blindness
Onchocerca volvulus
_____ may cause inguinal lymph node fibrosis and atrophy of overlying skin that leads to ‘hanging groin’
Onchocerca volvulus
AKA River Blindness
Location: Northern S. America, C. &W. Africa
Acquired by the bite of the Black fly (Simulium spp)
Onchocerca volvulus
AKA River Blindness
Location: Northern S. America, C. &W. Africa
Acquired by the bite of the Black fly (Simulium spp)
Onchocerca volvulus
Adults in subcutaneous nodules, unsheathed microfilariae in dermis
Symptoms: Nodules on head (SA), lower trunk (Africa), pruritic skin reactions, “leopard skin”, hanging groin, progressive blindness
Onchocerca volvulus
Actually a symptom of larval movement in tissues.
- Visceral will occur in gut tissues, caused by several species, of which ______ are best known
Toxocara spp
Cutaneous occurs under skin (often termed “creeping eruption”) and many species of worms may cause this (e.g. _____ and various hookworms)
Ascaris spp.
Actually a symptom of larval movement in tissues
May also occur in eyeball
(ocular larval migrans)
Ingestion of infective eggs is the root cause of the problem
Found wherever dogs and cats are found
Puppies can be infected via transplacentally or through breast milk
Caused by Toxocara canis and Toxocara cati
Pathogenesis
-Larval forms leave focal site and migrate through tissues to new sites to mature
Visceral Larval Migrans
Sites characterized by inflammation, damage, and pruritic skin lesions
Long term/deeper infections may have allergic conditions and toxemia reactions
Organisms may form granulomas in tissues
Cutaneous Larval Migrans
“Creeping Eruptions”
Creeping Larva Migrans
Why would you sometimes treat patients with filariasis with doxycycline?
A. To eliminate the symbiont Wolbachia
B. To reduce the edema swelling
C. To treat bacterial superinfections
D. To reduce their fever
A. To eliminate the symbiont Wolbachia
Which of the blood cells, when in high number, usually is an indication of a parasitic infection?
A. Lymphocytes
B. RBCs
C. Eosinophils
D. Neutrophils
C. Eosinophils
Bachmans?
Trichinella spiralis
Specimen processing
– Specimen of choice is muscle biopsy
– Skin test: Bachman and others
– Blood: ESR, eosinophil count
drink unfiltered water with infected copepod?
Dracunculus medinensis
Fly bite with adults in subcutaneous, produce sheathed microfilariae
Loa Loa
Adult in subcutaneous nodule, produce unsheathed microfilariae
Onchocerca volvulus
ingesting infective eggs near cats/dogs, mostly child less than 6 y/o
Toxocara (canis/cati)
