Ebola Reston Outbreaks

• The Mindanao, Philippines Outbreak
  
  

  
  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.

  
  Ferlite Farms
  Ferlite Farms is located in a 2.5 to 3-hectare area in Calamba, Laguna, Philippines, which is approximately 40 km South of Manila. Ferlite uses open cages as their holding facilities. Individual cages are used in their quarantine facility. Until 1996, Ferlite exported 1500 monkeys annually to the United States. The monkeys used for breeding come from Zamboanga and Iligan City. Supposedly, Ferlite quarantines the monkeys 30 days prior to shipping.
  
  References:
  
  • Miranda, M.E.G., et al. Seroepidemiological study of filovirus related to Ebola in the Philippines. The Lancet 1991; 337:425-26.
  • Philippines bans export of monkeys over U.S. scare. N and O Times.
  • WHO Ebola-Reston Investigation, Philippines - Update
  • Breeder wants his monkeys spared. CNN Interactive. April 18, 1996.

• The Reston, Virginia Outbreak
  
  On October 2, 1989, 100 cynomolgus macaques (Macaca fascicularis) from Ferlite Farms in Mindanao Island, Philippines were flown from Manila, through Amsterdam to New York, and then transported by truck to Hazleton Research Products' (HRP) Reston Primate Quarantine Unit in Reston, Virginia. These monkeys were placed in Room F of the Reston Unit on October 4. HRP's Reston Unit already had approximately 500 cynomolgus monkeys when this shipment arrived. There had not been any African species quarantined in the Reston unit for many years, ergo it is not possibile that the monkeys contracted Ebola from fomites contaminated by a prior shipment of monkeys. Because of the 1976 Marburg incident, all primates imported into the United States must be quarantined for 30 days to insure that they are disease free before they are released. In any transcontinental shipment of animals, a high attrition rate is to be expected due to this experience. However, this particular shipment of nonhuman primates had a far larger number of deaths in Room F than would normally have been expected. The HRP veterinarian conducted a few necropsies of the dead monkeys from this shipment in Room F and, based on the clinical symptomatology and on gross anatomy, made an initial diagnosis of simian hemorrhagic fever (SHF). SHF is a terrible disease in monkeys (fortunately it does not infect humans) and is easily transmitted amongst them. The HRP vet sent samples of the dead monkey tissue to United States Medical Research Institute of Infectious Diseases (USAMRIID) for conclusive diagnosis. SHF was isolated in the tissue cultures that HRP sent to USAMRIID. Before USAMRIID finished their diagnosis, HRP made the decision to euthanize all of the remaining monkeys in Room F to prevent possible further spread. During the 10 days following the euthanization of the monkeys in Room F, there were sporadic deaths in the remaining monkey population at Reston. The pattern of the deaths nor the pathology in the dead monkeys was indicative of SHF. The HRP vet became alarmed by this. Meanwhile, USAMRIID was conducting additional tests on the monkey tissue cultures and discovered that Ebola was also responsible for the Reston monkey deaths from an electron micrograph of damaged tissue from one of the dead Reston monkeys. Unfortunately, the pathogen was not contained by the euthanization of the monkeys in Room F. 29 additional monkeys in Room H had also died. The monkeys in Room H were from a separate shipment (but from the same supplier, Ferlite Farms) that had arrived at the Reston Unit on November 8.
  
  Were the Room H monkeys contracting the pathogen from the Reston Quarantine Unit or were they infected with the pathogen back in the Philippines? The Room F monkeys were euthanized on November 16. The Room H shipment of monkeys arrived on November 8. Both the Room F and Room H cynomolgus monkey shipments came from Ferlite Farms in the Philippines. Ferlite Farms was experiencing a hemorrhagic disease outbreak concurrently. It is likely that the Room H monkeys were sub-clinically harboring EBO on arrival. EBO has an incubation period ranging from five to seven days in nonhuman primates (personal correspondence, Anderson). The Room H monkeys arrived at the Reston unit while the Room F monkeys were still alive.
  
  On November 29, the Center for Disease Control (CDC) and the Virginia Department of Health met with USAMRIID, and a coherent plan of action was formulated to insure the safety of the community and the humane treatment of the Reston primates. Because of the threat that Ebola might spread to the remaining animals in the quarantine unit and that it might infect the staff, the remaining animals (~500) in Room H were euthanized on November 30, 1989. On November 28, 1989, Ferlite Farms, unknowingly, sent a shipment of EBO-infected cynomolgus monkeys to Philadelphia.
  
  Six of the 178 people who had contact with the infected monkeys at the Reston Quarantine Unit seroconverted. All six of the individuals worked with the primates. None of the six who seroconverted developed a filovirus-related illness. Of them, four (all of whom were animal handlers at one quarantine facility) had serologic evidence of recent infection with Ebola-Reston. It is likely that one of the four infected himself when he cut his finger while performing a necropsy on an infected monkey. The mode of transmission for the other three handlers is not known. The remaining two people were seropositive at low titer and had evidence of past infection. One of these two people is a worker at a facility that temporarily houses nonhuman primates before delivery to U.S. quarantine facilities and had had regular contact with quarantined nonhuman primates for three years. The second person was an employee at Hazleton's Texas Primate Center.
  
  CDC researchers conducted an additional study on the prevalence of seropositivity to filoviruses. They tested 550 people with varying levels of exposure to monkeys (or monkey tissues or body fluids) with an indirect immunofluorescence assay test (IFAT) and confirmed the results using Western blot. 42 of the 550 (7.6%) people tested were positive to at least one of the filoviruses (EBO-Z, EBO-S, EBO-R, EBO-CI, MBG). 26 of 266 (9.8%) import quarantine facility staff members were seropositive; 16 of the remaining 284 (5.6%) persons having contact with monkeys (or with monkey tissue or body fluids) outside of import quarantine facilities were seropositive. None of the 42 who tested seropositive reported having any illness believed to be caused by a filovirus.
  
  In order to assess the significance of the prevalence of the seropositivity in people who have contact with monkeys and their bodily fluids/tissues, the CDC conducted a cross-sectional study on the seroprevalence of filovirus on the serum from 449 adults in outpatient primary care facilities throughout the United States. Using the same IFAT and Western blot assays, of theses 449, 12 were positive (2.7%) (Morbidity and Mortality Weekly Report 39(24): 404-05, 1990).
  
  For further information on the EBO-R outbreak in Reston, Virginia, please see:
  
  • Peters, C.J. Virus Hunter: Thirty Years of Battling Hot Viruses Around the World. 1997.
  • Miller, RK. Update: Filovirus Infections Among Persons with Occupational Exposure to Nonhuman Primates. Morbidity and Mortality Weekly Report April 27, 1990:39(16);266,273.
    
  • Jahrling, P.B. et al. Preliminary report: isolation of Ebola virus from monkeys imported to USA. The Lancet 1990;335:502-05.
    
  • Dalgard, D.W. et al. Combined Simian Hemorrhagic Fever and Ebola Virus Infection in Cynomolgus Monkeys. Laboratory Animal Science 1992;42(2):152-57.
  
  
  

• The Alice, Texas Outbreak
  
  

  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 pages:
  

  Clinton urges Americans not to overreact on Ebola

  Levine, Jeff. Does importing primates push Ebola risk too high? CNN April 16, 1996

  The Texas Department of Health Ebola Page
  

  The Texas Department of Health "Question and Answers About the Ebola Disease in Monkeys in Alice, Texas" Page
  

  Texas Department of Health April 15, 1996 "Ebola Media Briefing"
  

  "Ebola-Reston Virus Suspected in Third Monkey" April 17, 1996 Press Release from the Texas Department of Health (TDH)
  

  "Test Results Negative on Monkeys" April 18, 1996 Press Release from TDH