BUG WEEK: Day 7.5- I forgot about tick-borne encephalitis

After 3 hours of lecture today on meningitis, meningoencephalitis, and encephalitis, I became aware of an omission on one of my posts. On 7/15 I listed the diseases carried by the Ixodes tick (AKA black-legged tick AKA deer tick), but I left out a strain of Flavivirus, which can cause tick-borne encephalitis. The interesting thing about this is that all other viral causes of encephalitis are transmitted by mosquito bites. West Nile virus is also a Flavivirus, and is probably the most commonly known strain in the US. (especially after the New York outbreak a few years ago)

Meningitis is inflammation of the meninges, which is one of the protective tissue layers of the central nervous system (brain and spinal cord). Encephalitis is inflammation of the brain tissue. Meningoencephalitis is both. TBE can present as any of the three. You'll have a patient with a fever, altered mental status, and mosquito or tick bites. They don't necessarily get the stiff neck that people with bacterial meningitis do.

Anyway, there are no skin findings and treatment is supportive, meaning there is no cure, but it is something to think about if you're in tick-infested country. Also, there is a rare association with neurological side effects similar to amyotrophic lateral sclerosis (Lou Gehrig's disease). I couldn't find much research on it, but it does exist in case reports. ALS is a neurodegenerative disorder where the motor neurons in both the central and peripheral nervous systems start to die. It is one of the only neurodegenerative disorders that has both upper and lower motor neuron symptoms.

Müller WK, Hilgenstock F. An uncommon case of amyotrophic lateral sclerosis with isolation of a virus from the CSF. J Neurol. 1975 Dec 2;211(1):11-23.Links

An atypical case of amyotrophic lateral sclerosis (ALS) is described, characterized by early manifestation, a long lasting course with asymmetry of the lesions, absence of bulbar symptoms in the presence of an otherwise very advanced symptomatology, and constant signs of an inflammatory reaction in the CSF which was the reason to initiate extensive virological studies, including procedures for virus isolation. A virus belonging to the TbE complex of arbovirus group B (tick-borne flavivures), was finally isolated from the CSF. About 70% of the ALS cases in Hamburg/W. Germany, examined for antibodies, apparently had contact with this virus. The antibody pattern found made it possible to explain this exceptional case.

I could only find a couple articles written specifically on this topic since 1975. They think that some of the antibodies produced in reaction to the virus end up attacking motor neuron cells.

This concludes BUG WEEK 2007.