What is the optimal method of diagnosis and patient management?
Halicephalobus also referred to as Micronema species is an emerging pathogen that can cause fatal meningoencephalitis in humans.
Recently, there have been two high profile cases of renal transplant recipients in press in the United Kingdom who received cadaveric kidneys infested with the nematode, Halicephalobus. Subsequently the patients developed severe meningoencephalitis as a consequence of this infestation and both of them died. Post-mortem examination confirmed the causative organism to be Halicephalobus.
My Medline search showed that there are five or six case reports published in literature which emphasise the zoonotic (equine) origin of this organism, its high mortality rate and difficulties associated in making an ante-mortem diagnosis.
I would appreciate your comments/expert opinion on the source, mode of transmission, diagnosis and patient management of this infestation.
Many thanks for your response.
Sayed S Bukhari MD, MSc, FRCPath
Consultant in Infection
Halicephalobus gingivalis is a free-living species of nematode and a facultative parasite of horses and humans. It has both an asexual and a sexual life cycle. It generally found in swampy environments and associated with manure. Infection is thought to occur through breaks in the skin or through mucous membrances
It is most probably present in rotting vegetation and soil and infects human in unsual circumstances. All cases that I am aware of have been immunosuppressed. The first case was a boy who fell through a manure spreader, not on immunosuppresion, but with severe injuries which would have caused severe challenge to the immune system. Note that horses are quite susceptible to this infection too. We presume it enters the body through lacerations which come into contact with rotting vegetation, though little is known about the organism.
Halicephalobus sp. can infect exotic spiders (Teraphosidae). Human bites by infected spider may be possible way of infection. Please see:
https://www.researchgate.net/publication/10711830_Oral_nematode_infection_of_tarantulas
Article Oral nematode infection of tarantulas [1]
Actually the nematode found in spiders is a true Panagrolaimus, not a Halicephalobus, though both are part of the same nematode family Panagrolaimidae. I have found Halicephalobus on the outside of seeds however. This suggests a possibility that an invertebrate might vector this related nematode as well. Two manuscripts on these different nematodes are close to submission.
Lynn Carta
I can recommend some recent publications concerning the topic.
C.Kok Lim et al. 2015. J. Clinical Microbiol. 53 (5): 1768-74;
B. Papadi et al. 2013. Am. J. Trop. Med. Hyg. 88 (6): 1062-4;
M. Eydal et al. 2002. Vet. Parasitol. 186 (3-4): 523-7.
Best wishes.
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