1. Venezuelan Equine Encephalitis Virus in MexicoPaul R. EarlFacultad de Ciencias BiologicasUniversidad Autónomo de Nuevo LeónSan Nicolás, NL, Mexico

2. Venezuelan equine encephalitis (VEE) is a mosquito-borne acute viral disease characterized by fever, chills, headache, back pain, myalgias, prostration and possibly nausea, often progressing to encephalitis. Crashing into the stall walls, a fence or a tree is typical of horses and can occur in humans. An equine pressing its head against something solid is parallel to a man holding his head with both hands. VEE is much more dangerous for equines (horses, mules and donkeys) than for man. The VEE strains most involved are IAB, AC and most importantly IE.

3. In Mexico, over 200,000 equines died in 1971. This was reported. However, that enormous Culex-transmitted epidemic was from 1969 to 1975. Far far more deaths occurred, certainly way over 2 million. Also, more than one virus species was involved, e. g., St Louis Encephalitis virus (SLE).

4. Why so misreported ? FIRST: Do not know. SECOND: Did not dutifully observe, count and record. THIRD: Hiding the facts is often a routine of public health. FOURTH: No index of suspicion therefore no VEE diagnosis in people. # 3 includes the bearer of bad tidings—the innocent reporter of bad news is unpopular.

5. A very important fact is that in Mexico the Sectretaria de Salud is completely separated from Patología Animal, which is part of the Secretaría de Agricultura. Patología Animal has over 100 laboratories throughout the country, but contacts between medical and veterinary interests are rare indeed. In the 70s, laboratories had only vaccine. They did not made viral identifications. They did not have sentinels, chicks or hamsters. They did not have mosquito light traps. The same impoverished laboratory conditions prevail in 2004.

6. How many deaths ? No one knows.We can say—at least—that in 1969-74 in Mexico—in all 32 states there were 200,000-2,000,000 plus equine deaths and some human deaths. This lecturer was vaccinating horses in Puebla and Veracruz in 1971-74. The encephalitis virus status has not changed in 30 years, true also for tropical diseases.

7. A VEE vaccination campaign was used.All efforts were then placed on vaccinating equines. Some cattle of many infected died of VEE also. The order of encephalitis virus may have been: 1/ VEEV, 2/ STLV, 3/ EEEV then 4/ WEEV. However, the encephalitis is usually considered as caused by VEE only. Why do you suppose that is ? A vaccine failure may be then caused by some other virus.

8. HistoryDuring the 1930s, 3 distinct but antigenically related viruses were recovered from sick horses and were shown to be previously unrecognized agents of severe equine encephalitis. Western equine encephalitis (WEE) virus was isolated in the an Joaquin Valley in California in 1930, Eastern equine encephalitis (EEE) virus in Virginia and New Jersey in 1933, and Venezuelan equine encephalitis (VEE) virus in the Guajira peninsula of Venezuela in 1938.

9. Biological WarfareVEE, like EEE, is a potential biowarfare weapon, even without genetic engineering, that could intensify its lethality. An aerosol spray released from a single airplane would infect thousands of people in thousands of squared kilometers.Alphaviruses, especially the equine encephalomyelitis viruses, lend themselves very well to warefare. Although other encephalitic viruses could be considered as potential weapons, few possess as many characteristics for strategic weapons development as the alphaviruses.

10. These viruses can be produced in large amounts in inexpensive and unsophisticated systems. They are stable and infectious for humans as aerosols. Strains are available that produce either incapacitating or lethal infections, having of multiple serotypes of VEE and EEE viruses.Just as they have little vector or host specificity in nature, the alphaviruses replicate readily at very high titers in a wide range of cell types and culture conditions in vitro. The same is true for Flavididae viruses. Virus titers of 1 billion infectious units/ml are reached.

11. Togaviridae are close to Flaviviridae.Clinical symptoms are similar to those of many other viral zoonoses that cause fever and headache caused by a Flavivirus. VEE is caused by an enveloped single-stranded RNA virus of the Togaviridae family, Alphavirus genus. Formerly, this was group A arboviruses. The VEE RNA is enveloped in an icosahedral coat structure, having a diameter of over 60 nm. Surface spikes are recognized by host receptors. Six subtypes (I, II, III, IV, V and VI) have been identified.

12. The core is enveloped by a lipid bilayer that is penetrated by 80 glycoprotein spikes, arranged as an icosahedral surface lattice. These spikes are also arranged in a T=4 lattice that is in register with the internal nucleocapsid. Each spike is a trimer of heterodimers that extends to a viral radius of 345 Å with a on its globular extremity. The heterodimer consists of 2 glycoproteins, E1 and E2, whose C-terminal ends protrude on the cytoplasmic side of the membrane by 2 aminoacids and between 31 and 33 aminoacids, respectively.

13. Alphaviruses are small enveloped viruses that package an ~11.5-kb, positive-sense, single-stranded RNA genome. The viral genome encodes 4 nonstructural (nsP1, nsP2, nsP3, and nsP4) and 5 structural (capsid, E1, E2, E3 and 6k) proteins. This simple protein composition makes alphaviruses model systems ideal for studying enveloped virus assembly and structural electron cryomicroscopy. Image reconstruction of Sindbis, Semliki Forest, Ross River and Aura viruses show that the envelope glycoproteins are arranged on the outer surface of the virus as 80 trimers in a T=4 icosahedral lattice.

14. How do the encephalitis virus spread? The devastating outbreak in Mexican equines was from 1969 to 1975 involving the deaths of millions of equines. Epizootic control was obtained by a large-scale national equine immunization program. Mexico, Central America and Panama had subtype IE. VEE reached Texas in 1971. ). The original epizootic VEE viral isolate made in Venezuela in 1937 was caused by a strain of variant I-A/B, which was also responsible for the 1969-72 plus epizootics in Ecuador, Central America, Mexico and Texas. Epizootics during the 1960's and 1970's, and in 1992-3 and 1995 in Colombia and Venezuela were caused by variant I-C.

15. The main sources of VEE for Mexico, e. g., IE , are Ecuador & Colombia by mosquitoes via East Pacific hurricanes. Still, an Atlantic hurricane in the Caribbean can move mosquitoes west off Venezuela into Mexico, but most of the Atlantic hurricanes—6 in the first half of 2004—go straight north, often along the Gulf coast into the US.

16. VEE seems “somewhat” restricted to horse—mosquito—horse, and even man—mosquito—man rather than invoving birds, rodents, etc., although they are like mice infectible. Then suppose a new outbreak is imported into Mexico by wind-borne mosquitoes from northern South America, not generated endemically. The new epidemic may be coming from the Eastern Pacific Hurricane Center. An epidemic jump at hurricane speeds from Colombia or Venezuela is easy to visualize into Oaxaca or straight north into Baja California, Mexico and through into Arizona-to-California, US. The same sources might produce winds on another occasion that can reach Hawaii !

17. Hurricane season influencesThe transmission of VEE and other viruses via mosquitoes is dominated by the Eastern Pacific hurricanes, although of course controlled often by the Atlantic hurricane winds.BOTH Pacific and Atlantic hurricanes travel north along the Veracruz coast into Texas and some into the other US Gulf states and of course some reach Florida.

18. The viral epidemiology CHANGES EXACTLY (!) as the rainfall does. The main influence is the Atlantic—Pacific hurricane winds changing their directions and forces. Let us IMAGINE an unlikely (?) strong hurricane from Colombia going due north. It would hit La Paz, of course. It would cover the Gulf of California and western Sonora. It would reach California, Nevada and Arizona in the US. COULD such a viral epidemiology occur, or not? What was the season? What is the time schedule? What were the wind speeds? How long did ‘Imagine’ last? How far did it reach? What micro- and macroorganisms was it carrying? Did Colombian mosquitoes breed in Mexico or in the US?

19. The Alameda EEE episodeIn June, 1996, Eastern Encephalitis Virus (EEV) arrived in Oaxaca, Mexico from Colombia apparently. It was in Veracruz by July and Tamaulipas (Tamps) by September, carried by mosquitoes in hurricane winds from the Pacific. Mexican veterinarian had to send samples to the US National Disease Laboratory, Ames, Iowa to be identified, because of lack of virus facilities. This epidemic became selflimiting in October at Alameda, Tamps. Veterinarians in Tamps had tried to stop this outbreak by vaccinating a ring of horses with the old vaccine that missed completely. What was really lost? Time. Why?

20. The Colombian EEE virus entered Oaxaca in June and smouldered out in Tamps in October. The rainy season was over. Did the Gulf winds reverse? There were July & August equine deaths in Veracruz, yet no human deaths were recognized. Signs for “Vaccinate your horse” were up on Veracruz highways. Of course, that would have been a wrongway vaccine !Was there time for Colombian EEE culicines to breed in Mexico? Is it really the lack of time for a sexual cycle, and the onset of autumn drought that did stop the EEE outbreak. Were these mosquitoes possibly 5-6 months old?

21. More virus reference labs in both human and veterinary medicine, and sharing facilities are needed in Mexico. Sentinels might be permanently maintained in the cities of Merida, Yucatán, Oaxaca, Oaxaca, Tapachula, Chiapas and La Paz, Baja California del Sur. Virus installations have high maintenance costs and require expert technicians. The bacterial techniques and standard equipment may not be present in some clinics. Veterinarian laboratories should have improved communications with medical laboratories. Upgrading for better human and animal health seems needed despite the high costs of modern laboratories and reagents.

22. More than equine encephalites is involved in improving rural life. VEE is a highlight of tropical medicine, though primarily a veterinary topic. Hoof-and-mouth disease in cattle in 1953 was the rural tragedy before VEE. NOW LONG-STANDING AND IMPOVERISHED CHAGAS DISEASE IS A RURAL TRAGEDY, HOWEVER HIDDEN IT MAY BE. Will the next EEE episode kill people ?What might the next DISASTER be? An interesting question because it also asks: “How much MONEY will be spent on surveillance and vector control?”