Manual of basic techniques for a health laboratory - libdoc.who.int

4. Parasitology 165Table 4.8 Characteristics of common human filarial parasitesCharacteristic B. malayi B. timori L. loa M. ozzardi M. perstans M. streptocerca O. volvulus W. bancroftiGeographical South-east Asia, Lesser Sunda Central and Central and Central and Central and Africa, Central Tropical anddistribution Indian islands, Timor West Africa South America, West Africa, West Africa and South America subtropicalsubcontinent Caribbean South America countriesVectors Mosquitoes Mosquitoes Tabanid flies Biting midges Biting midges Biting midges Blackflies Mosquitoes(Anopheles and (Anopheles spp.) (Chrysops spp.) (Culicoides spp.) (Culicoides (Culicoides spp.) (Simulium spp.) (Culex, Aedes,Mansonia spp.) and blackflies spp.) Anopheles and(Simulium spp.) Mansonia spp.)HabitatAdults Lymphatic Lymphatic Subcutaneous Subcutaneous Mesentery Dermis Subcutaneous Lymphaticsystem system tissues, orbit tissues tissues systemMicrofilariae Blood Blood Blood Blood Blood Skin Skin BloodPeriodicity of Nocturnal a Nocturnal Diurnal Aperiodic Aperiodic NA NA Nocturnal bmicrofilariaeMorphology of microfilariaeSheath Present Present Present Absent Absent Absent Absent PresentLength (mm) 175–230 in 265–325 in 230–250 in 160–205 in 190–200 in 180–240 in skin 300–315 in skin 240–300 insmears; smears; smears; smears; smears; snips snips smears;240–300 in 2% 330–385 in 2% 270–300 in 2% 205–250 in 2% 180–225 in 2% 275–320 in 2%formalin formalin formalin formalin formalin formalinWidth (mm) 5.0–6.0 4.4–6.8 5.0–7.0 3.0–5.0 4.0–5.0 5.0–6.0 5.0–9.0 7.5–10.0Tail Tapered; Tapered; Tapered; nuclei Long, slender, Bluntly Bluntly rounded, Typically flexed; Tapered;subterminal and subterminal and irregularly pointed; rounded; nuclei bent into a hook; tapered to point; anucleateterminal nuclei terminal nuclei spaced anucleate to end nuclei to end anucleatewidely separated widely separatedKey features Long head space; Long head space; Sheath Small size; long Small size; Slender shape; Flexed tail; Short head space;sheath stains pink sheath unstained unstained in slender tail; blunt tail filled hooked tail filled occur in skin and sheath unstainedin Giemsa; terminal in Giemsa; Giemsa; single aperiodic with nuclei; with nuclei; occasionally in in Giemsa; bodyand subterminal terminal and row of nuclei to aperiodic occur in skin urine or blood in smoothnuclei subterminal nuclei end of tail after treatment curves; dispersednucleia Nocturnally subperiodic in Indonesia, Malaysia, parts of the Philippines and Thailand.b Diurnally subperiodic in New Caledonia and Polynesia; nocturnally subperiodic in rural areas of Thailand.