The outbreak of EBO-R in the United States caused by infected monkeys in the United States prompted the Philippine government to investigate whether the workers in the primate facilities were at risk for contracting EBO-R, and, if so, to what degree they were at risk. The investigative team studied 186 people, 48 of whom were from wildlife collection areas and the remaining 138 were from the four primate export facilities in the area (Ferlite Farms being one of the four). Twelve of the 186 people tested had serological evidence of infection with EBO-R. 22% of the workers at Ferlite Farms had positive IFAT (indirect fluorescent antibody test) titers, which was significantly higher than at the other three export facilities. Of the five employees in Ferlite's animal hospital, four had positive IFATs. Workers in the hospital had more positive titers than the rest of the workers at Ferlite Farms.
All of the monkeys at Ferlite were killed after this outbreak of EBO-R in 1989.
On January 31, 1990, Ferlite Farms sent a shipment of 100 macaques to Hazleton's Texas Primate Center (TPC) in Alice, TX. A day later, 100 monkeys from Ferlite were also sent to HRP's Reston Unit. Within the first week of arrival, the monkeys at both facilities had clinical signs that were identical to the signs during the first Reston outbreak. The two separate shipments of monkeys from Ferlite to Reston and Alice had no contact after they left Ferlite Farms. From February 1 through March 15, 46 of 52 animals in one of the quarantine rooms died. The surviving six tested positive for filovirus. Necropsy samples from the TPC monkeys were sent to the Center for Disease Control (CDC) for conclusive diagnosis. The CDC determined that the monkeys were co-infected with SHF and Ebola. The cages at TPC were numbered horizontally and stacked in two tiers. In this quarantine room at TPC, monkeys had a 40% chance of dying if they were horizontal from a neighbor who had EHF, and if they were vertical from a neighbor who had EHF, they had a 26% chance of dying. "Because animals were consistently fed, handled, and treated in ascending order by cage number, these data suggest that handling procedures may be implicated in transmission" (Hendricks, KA et al. Filovirus Outbreak Among Philippine Nonhuman Primates in South Texas).
Texas outbreak, number 2. In March of 1996, 100 colony raised macaques from Ferlite Farms were shipped from Manila to Houston by way of Hong Kong and Rome. These monkeys arrived to TPC on March 21. On March 27, one of the monkeys from this shipment showed signs of illness and died on March 30. Necropsy of this dead monkey indicated a pneumonic process, and the liver tested positive for Ebola. On April 10, a second monkey that was housed at the opposite end of the block of cages from the index case became ill. On April 13, this monkey's serum tested positive for Ebola and was sacrificed. (20 days after the monkey arrived and 13 days after the incubation period was over if it contracted EBO from the Philippines).
If the monkeys were quarantined for 30 days prior to being shipped to the US, how come they developed EBO-R once they reached the US? The incubation period of EBO in nonhuman primates is 5-7 days.
For news items regarding the outbreak in Alice, Texas, please see the following