Tissue and Filarial Nematodes Flashcards
Trichinella spiralis (Trichinosis) General Information
- Organism extensively distributed throughout a wide range of mammalian hosts (bear, walrus, deer, pig)
Trichinella spiralis adult
1) Female: 3-4 mm (length), esophagus about one half as long as the body
2) Male: 1.5 mm (length) with conical projection at posterior end
Trichinella spiralis Diagnostic Stage
Larvae is found coiled in musle with nurse cell
Diagnostic stage
Trichinella spiralis Pathology
Three Stages
- Intestinal = malaise, mild fever, anorexia, diarrhea
- Muscular = muscle pain and tenderness, dyspnea, eye pain, problems with chewing, swallowing, breathing, etc
- Larval migration - edema of eyelids, retinal hemorrhage, conjunctivitis, rash, splinter hemorrhages
Trichinella spiralis Diagnostic Stage
- Muscle biopsy and detection of larvae
- Serologic test (bentonite flocculation)
- Examine suspect meat - use artificial digestion technique to release larvae
Dracunculus medinensis General Information
- “Fiery Serpent”
- Organism is worldwide and endemic in India and Pakistan; Africa has the highest incidence
Dracunculus medinensis Life Cycle
1) Larvae are swallowed with infected copepod
2) Freed in small intestine
3) Penetrate intestinal wall
4) Enter the subcutaneous tissue and migrate to lower extremities
5) Adult worm forms in extremities and creates a blister
6) Blister ruptures and the larvae are released into the environment
Dracunculus medinensis adult
Female: up to one meter in length
Male: small and inconspicuous
Dracunculus medinensis Pathology
Three Issues
- Skin = tenderness at site of blister, itching, nausea, diarrhea
- Worms removed during rupture = healing occurs, no problems
- Worm broken = possible cellulitis, secondary arthritis and synovitis
Dracunculus medinensis Diagnostic Stage
Diagnosis
- Formation of cutaneous lesion with appearance of adult worm
- X-rays for calcified worms
Treatment
- Metronidazole
Wuchereria bancrofti General Information
- Found in tropcis and subtropics (Africa, Near East, Far East, Southeast Asia, Central and South America)
- Transmission is human to human (only known reservoir host)
Wuchereria bancrofti adult
- Actively move about in lymph or blood
- 244-296 um in length
- No nuclei at tailtip
- Sheath present
- Demonstrate nocturnal periodicity with highest concentration of organisms in blood at night between 10 pm and 2-4 am
Wuchereria bancrofti Pathology
Two Stages:
- Acute = inflammation of lymph vessels/nodes (especially genitals and breasts), insomnia, nausea, anorexia
- Chronic = Elephantiasis, especially in genital area
Wuchereria bancrofti Diagnostic Stage
- Detection of microfilariae in blood
- Sheath will not stain adequately with Giemsa stain
- Nocturnal periodicity - collection of blood best between 10 pm and 2 am
- Delafield’s hematoxylin stain will stain sheath
Brugia malayi General Information
- Found in India, Malaysia, Thailand, Burma, Vietnam, coastal areas of China, Taiwan, South Korea, Japan, Borneo, and Indonesia
- Other hosts include dogs, cats, monkeys, and baboon
Brugia malayi adult
Microfilariae
- 177-230 um in length
- Sheathed
- Swollen tail with subterminal and small terminal nuclei at tip of tail
Brugia malayi Pathology
- Similar to W. bancrofti
- Lymphadenopathy and lymphadenitis
- Elephantiasis in lower extremities
- Genital involvement rare, hydrocele and chyluria
Brugia malayi Diagnostic Stage
- Detection of microfilariae in blood (Giemsa stain)
- Nocturnal periodicity
- Two peaks often occur between 8 pm and 4 am
Loa loa General Information
- Found in Western and Central Africa
- Mainly in rainforest areas of Sudan, Congo Basin, and West Africa
- Humans are the only known reservoir host
Loa loa forms
Microfilariae
- 250-300 um in length
- Sheathed organism
- Nuclei are continuous to the tip of the tail
Adult (female) can be seen under the conjunctiva of the eye or passing over the bridge of the nose
Loa loa Pathology
Temporary symptoms
Calabar or fugitive swellings are painful, itching, and inflammatory reaction, found anywhere on body
Loa loa Diagnostic Stage
- Patient history
- Calabar swellings
- Diurnal periodicity between 10 am and 2 pm
- Detection of worm migration in eye or across nose
Treatment - Involves surgical removal of adult worms from eye or calabar swellings across the bridge of the nose
- Drugs can be used to eliminate the worm
Onchocerca volvulus General Information
- Found in tropical zones of Africa and Central and South America, Mexico, and Guatemala
Onchocerca volvulus adult
Microfilariae
- 221-287 um in length
- No sheath
- Nuclei do not extend to tip of tail
- Life span of up to two years
Onchocerca volvulus Pathology
Two Types of Infection
- Light (3-15 mos) = asymptomatic, worms free in intestine
- Heavy = Dermatitis or Subcutaneous nodules containing adult worms
Blindness is caused by ocular lesions
Onchocercoma volvulus Diagnostic Stage
- Detection of microfilariae in skin (skin snips), rarely found in blood, urine, or sputum
- Find Onchocercomas and the adult worms within the fibrotic tissues
Treatment - Surgical removal of detectable nodules
- Drugs are available for treatment
Mansonella ozzardi/perstans General Information
M. perstans
- Central/South America (from Panama to Argentina), Africa, West Indies
- Reservoirs include humans, gorillas, and monkeys.
M. ozzardi - Yucatan, Panama, Central/South America, West Indies.
- Humans are the only known reservoir
Masonella Morphology
M. perstans
- 190-200 um in length
- Adult worms are found in body cavities (peritoneal, pleural)
- Microfilariae is unsheathed and has nuclei in the top of the tail
M. ozzardi
- 173-240 um in length
- Microfilariae is unsheathed
- Nuclei do not extend to tip of tail
- Male and Female worms live in the subcutaneous and connective tissues
Masonella Pathology
1) Both Considered nonpathogenic
2) Usually asymptomatic
3) May cause mild allergic reaction; eosinophilia is common
Masonella Diagnostic Stage and Treatment
- Detection of microfilariae in blood
- No periodicity (nonperiodic)
- Must be differentiated from other blood borne microfilariae
Treatment - No treatment needed for asymptomatic cases
- Symptomatic cases can be treated with drugs
Trichinella spiralis Infectious Stage
Ingestion of encysted larvae from undercooked meat: mainly pork
Wuchereria bancrofti Infectious Stage
Transmission via bite of mosquito (Anopheles or Culex)
Brugia malayi Infectious Stage
Transmission via bite of mosquito (Anopheles or Mansonia)
Loa loa Common Name
African Eyeworm
Loa loa Infectious Stage
Transmission via bite of sand fly, deer fly, or chrysops
Onchocerca volvulus Common Name
River Blindness
Onchocerca volvulus Infectious Stage
Transmission via bite of black fly (simulium) or buffalo gnat
Mansonella ozzardi/perstans Infectious Stage
Transmission via bite of midges or gnats (Culicoides)
