On the Etiology of Tropical Epidemic Neuropathies.

To the Editor: In a recent report of an epidemic of optic neuropathy in Dar es Salaam, Tanzania (1), Dolin et al. state that the disease is clinically identical to one of the forms of epidemic neuropathy found in Cuba between 1991 and 1993 (2). Cases of peripheral neuropathy have been part of both epidemics (1,2). Both epidemics occurred in nutritionally deficient populations (1,3).

Dolin et al. state that the cause of the Tanzanian epidemic is unknown and probably difficult to establish; however, we believe findings from the Cuban epidemic could be used to study the etiology of this and other tropical epidemic neuropathies.

In Cuba, several research groups isolated and characterized an enterovirus in the cerebrospinal fluid (CSF) of epidemic neuropathy patients (4,5). Enterovirus sequences were found in CSF of 40 (36%) of 111 epidemic neuropathy patients versus 1 (8%) of 12 control surgical patients (p [is less than] 0.01, chi-square test with 2 x 2 contingency tables) (5). Recently, this enterovirus has been shown to form quasispecies, which could account for altered biologic properties (de la Fuente et al., submitted for pub.). We thus propose that epidemic neuropathy has a nutroviral etiology: Nutritional deficits and stress make the population more likely to become ill after infection with enterovirus quasispecies with altered biologic properties.

The relationship between the host's nutritional status and virus evolution could be key in understanding the cause of epidemic neuropathy, the Tanzanian epidemic of optic neuropathy, and other tropical epidemic neuropathies. Etiologic factors must be identified before appropriate intervention and treatment strategies can be implemented.

References

(1.) Dolin P J, Mohamed AA, Plant GT. Epidemic of bilateral optic neuropathy in Dar es Salaam, Tanzania. N Engl J Med 1998;338:1547-8.

(2.) The Cuba Neuropathy Field Investigation Team. Epidemic optic neuropathy in Cuba--clinical characterization and risk factors. N Engl J Med 1995;333:1176-82.

(3.) Roman GC. On politics and health: an epidemic of neurologic disease in Cuba. Ann Int Med 1995;122:530-3.

(4.) Mils P, Pelegrino JL, Guzman MG, Comellas MM, Resik S, Alvarez M, et al. Viral isolation from cases of epidemic neuropathy in Cuba. Arch Pathol Lab Med 1997; 121:825-33.

(5.) Rodriguez MP, Alvarez R, Garcia del Barco D, Falcon V, de la Rosa MC, de la Fuente J. Characterization of virus isolated from the cerebrospinal fluid of patients with epidemic neuropathy. Ann Trop Med Parasitol 1998;92:97-105.

Jose de la Fuente and Maria P. Rodriguez Centro de Ingenieria Genetica y Biotecnologia, Havana, Cuba