Diagnosic Dilemma No. 15 


Contributor: Emeritus Professor John Goldsmid, University of Tasmania

 
The nematode egg shown in Fig. 15.1 was recovered from a routine stool specimen from an African male from Zimbabwe.
Image 1
Fig. 15.1 - Egg recovered from stool specimen
The eggs were measured and found to be approximately 85 x 52 mu in size.

A Harada-Mori larval culture was carried out and after 10 days, infective larvae as shown in Fig. 15.2 were recovered

Image 2
Fig. 15.2 - Infective larvae recovered after 10 days culture

The patient was treated with albendazole and adult worms about 8-10 mm long as shown in Fig. 15.3 were found in the faeces passed after treatment. A photomicrograph of the anterior end of one of the worms is shown in Fig. 15.4

Image 3
Fig. 15.2 - Infective larvae recovered after 10 days culture
Image 4
Fig. 15.4 - Photomicrograph of anterior end of one of the recovered worms


What is your diagnosis?



 


The worm infecting this patient was the False Hookworm, Ternidens deminutus.

This nematode is widespread in non-human primates in(eg baboons; vervet monkeys) in southern Africa and is a common zoonotic infection of humans (Goldsmid 1974, Goldsmid 1983, Goldsmid 1991).
Much is unknown about this worm including its mode of transmission and its exact prevalence in humans. T. deminutus is also recorded from Asian monkeys and whilst reliable records from humans in Asia are rare (Goldsmid 1983, Goldsmid 1991), at least one case of human infection has been reported from Thailand (Hemschrichart, 2005), though this was not differentiated from Oesophagostomum species by molecular means.
The clinical effects on the human host are also not well understood but are most probably load related (Goldsmid 1983, Goldsmid 1991).
Because of the similarity of the Ternidens egg to that of the hookworms and related species (Goldsmid 1983, Goldsmid 1991, Goldsmid 1968) (Fig. 15.5), misdiagnosis is probably common. For identification, measurement of egg size can allow differentiation between hookworm and T. deminutus (Goldsmid 1983, Goldsmid 1991, Goldsmid 1968). Hookworm eggs are about 70 x 40 um whilst eggs of T. deminutus are about 84 x 51 um in size (Goldmsid 1968, Beaver 1984). Identification of infective larvae using larval culture techniques (Goldsmid 1983, Goldsmid 1967) (Fig. 15.6) or collection of adult worms post treatment can also allow species identification of Ancylostoma duodenale, Necator americanus, Ternidens deminutus and other “hookworm-like” species (Goldsmid 1974, Goldsmid 1983).
Image 5
Fig. 15.5 - Comparative size of hookworm like eggs recovered from human faeces in Africa
Image 6
Fig. 15.6 - Filariform larvae of “hookworm-like” species
Ad: Ancylostoma duodenale Na: Necator americanus To: Trichostrongylus species Ss: Strongyloides stercoralis Rh: Rhabditis species Td: Ternidens deminutus Osp: Oesophagostomum species


 
References:
Goldsmid, JM. The intestinal helminthzooses of primates in Rhodesia. Ann Soc Belg Med Trop. 1974; 54:87-101.

Goldsmid, JM. Ternidens deminutus infection. In: Handbook Series in Zoonoses. Steele, H (Ed). Section C. Parasitic Zoonoses. Vol 2.1983. Boca Raton. Florida. CRC Press. 269-288.

Goldsmid, JM. The African Hookworm Problem. In: Parasitic Helminths and Zoonoses in Africa. Macpherson, CNL and Craig, PS (Eds). 1991. Unwin Hyman. London.101-137.

Hemschrichart, V. Ternidens deminutus infection: first pathological report of a human case in Asia. J Med Assoc Thailand. 2005; 88:1140-1143

Goldsmid, J.M. The differentiation of Ternidens deminutus and hookworm ova in human infections. Trans R Soc Trop Med Hyg. 1968; 62:109-116

Beaver, P.C., Jung, R.C. and Cupp, E.W. Clinical Parasitology.1984. 9th Edition. Philadelphia. Lea and Febiger.

Goldsmid, J.M. Ternidens deminutus Railliet and Henry (Nematoda): A diagnostic problem in Rhodesia. C Afr J Med. 1967; 13:54-58.




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