Global Health Pre-Trip Session
Helminthic infections seen in developing nations:
Neglected Tropical Diseases!
Paul M Southern, MD, DTM&H
2013
Diseases to be covered
Ascariasis: Ascaris lumbricoides
Echinococcosis (cystic hydatid): Echinococcus granulosus
Hookworm: Ancylostoma duodenale, Necator americanus
Lymphatic filariasis: Wuchereria bancrofti, Brugia malayi, B. timori
Onchocerciasis: Onchocerca volvulus
Schistosomiasis: Schistosoma mansoni, S. haematobium, S. japonicum, S. intercalatum, S.
mekongi
Strongyloidiasis: Stongyloides stercoralis
Taeniasis: Taenia solium, T. saginata, cysticercosis
Trichuriasis: Trichuris trichiura
Diseases NOT covered
Enterobiasis (pinworm): Enterobius vermicularis
Filaria (others): Loa loa, Mansonella ozzardi, M. perstans, M.
streptocerca, Dirofilaria spp.
Intestinal cestodes (rarer): Hymenolepis nana, H. diminuta, Dipyllidium
caninum, Diphyllobothrium latum, agents of Sparganosis
Intestinal nematodes (rarer): Capillaria philippinensis, Trichostrongylus
spp.
Other trematodes: intestinal, liver, lung
Tissue nematodes: many
Not covering ANY protozoa, despite their great importance
Global Estimates of number of soiltransmitted helminths (millions), WHO
Ascariasis:
1,222
Trichuriasis:
795
Hookworm:
740
Strongyloidiasis: ~500*
* = incomplete data
Estimated number of DALYs lost
(thousands) by cause [helminths only]*
Schistosomiasis: 1,707 worldwide, 1,502 Africa
Lymphatic filariasis: 5,941 worldwide, 2,263 Africa, 3,525
SE Asia
Onchocerciasis: 389 worldwide, 375 Africa
Ascariasis: 1,851 worldwide, 915 Africa, 404 SE Asia
Hookworm: 1,092 worldwide, 377 Africa, 286 SE Asia
* WHO data; DALY = disability-adjusted life years
Cost-effectiveness of controlling neglected
tropical diseases (Cost per DALY averted in
$US)
Lymphatic filariasis: 35 – 370 (depends on region)
Schistosomiasis: 10-23, or as much as 844 (depends on
strategy)
Onchocerciasis: 9
Soil-transmitted helminths: 2-11 (mass school treatment)
(Includes hookworm, ascariasis, whipworm)
WHO-recommended anthelminthic drugs for
treatment or prevention
Disease
Albendazole
Mebendazole
Diethylcarbamezine
Ivermectin
Praziquantel
Levamisole
Pyrantel
Ascariasis
+
+
-
(+)
-
+
+
Hookworm
+
+
-
-
-
+
+
Lymphati
c filariasis
+
-
+
+
-
-
-
Onchocerciasis
-
-
-
+
-
-
-
Schistosomiasis
-
-
-
-
+
-
-
Trichuriasis
+
+
-
(+)
-
(?)
(?)
Other
flukes
-
-
-
-
+
-
-
Strongyloidiasis
+
(+)
-
+
-
-
-
Taeniasis
-
-
-
-
+
-
-
Morbidity associated with soiltransmitted helminths*
Intestinal bleeding:
Hookworm
Malabsorption syndromes: Ascariasis
Competition for micronutrients: Ascariasis
Impaired growth: Ascariasis
Anorexia, reduced food intake: Ascariasis
Diarrhea or dysentery: Trichuriasis
Cognitive impairment: Trichuriasis
Intestinal obstruction: Ascariasis
Rectal prolapse:
Trichuriasis
* Montresor, et al.TRSTMH.2010;104:129-32
Taenia
Taenia solium
Taenia saginata
T. solium
T. saginata
CLASSIFICATION OF PATHOGENIC AND
COMMENSAL HUMAN PARASITES
B. TISSUE CESTODES (Larval)
1.
2.
3.
4.
5.
Taenia solium (cysticercoisis)
Echinococcus granulosus (hydatid cysts)
Echinococcus multilocularis (alveolar hydatid)
Multiceps spp. (Taenia multiceps) “Coenurosis”, “Coenuriasis”
Spirometra mansoni, Spirometra mansonoides, others (Sparganosis)
ECHINOCOCCOSIS
(Hydatid Disease)
Causative Agents:
Echinococcus granulosus
Unilocular, simple cysts, cystic hydatid
Echinococcus multilocularis
Alveolar, complex cysts
Echinococcus oligarthrus}
Echinococcus vogeli }
Manifestations:
Polycystic hydatid
Cysts in liver, spleen, lung, bone, kidney, muscles, brain,
myocardium
Diagnosis:
Clinical history and examination, imaging techniques,
serological tests (ELISA, CF, IHA, arc-5 double-diffusion
assay, enzyme-linked immunotransfer blot), hydatid sand
in cyst at surgery
Treatment:
Surgery, pre-and postoperative albendazole with or
without praziquantel (scolicidal); albendazole dosage 400
mg BID X 28 days, repeat if necessary; PAIR
Echinoccosis granulosus
CT Scan of Abdomen,transverse
CT Scan of Abdomen, vertical
View at Surgery
Surgical specimen from prior patient
Intestinal obstruction due to Ascaris lumbricoides
Hookworm Life Cycle
Larva currens
Rhabditiform larva of Strongyloides stercoralis
Strongyloides stercoralis on stool
culture plate
P
A
Taken from:
Wuchereria bancrofti microfilaria in peripheral blood
tip
nuclei
sheath
Brugia malayi microfilaria
Brugia malayi, separation of last nuclei
Onchocerca volvulus, life cycle
Geography of epidemiology
Black fly, (Simulium damnosum)
Schistosome Map, 2006
Major Schistosomes, life cycle
Egg Schistosoma intercalatum
Schistosoma spp. epidemiology
Epidemiology of S. mansoni and S. haematobium in
Africa
Cote d’Ivoire
Senegal
Epidemiology of S. mansoni and S.
haematobium in Africa
Beautiful Lake Malawi: notorious as a prime site for
transmission of schistosomiasis
S. japonicum, mekongi
Similar pathogenesis as S. mansoni
More CNS lesions in S. japonicum
Salmonella bacteremic infections may
occur with most species of
Schistosoma
S. Japonicum Asia
S. japonicum, Asia
Transmission of S. japonicum in
China
Agricultural irrigation
ditch
S. japonicum, S. mekongi
The End