North Florida Field Office
Service memo clearing quarantined
manatees
for release back into the wild
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North Florida Field Office Service memo clearing quarantined |
December 15, 2008
Memorandum for the Record
From: Nicole Adimey, USFWS, Manatee Rescue, Rehabilitation and Rescue Program Coordinator
Subject: Fish and Wildlife Service position regarding captive manatees with papilloma virus
Introduction
The purpose of this memo is to present the history of papilloma virus (PV) within the captive and wild manatee population, present results of research conducted to better understand PV, outline recommendations made by an expert disease panel, and document the actions and decisions made by the Service regarding PV and captive manatees.
History
The North Florida Ecological Services Office in Jacksonville, Florida has recovery lead and administers the daily management of the Florida manatee. One recovery activity for this species is the implementation of the Manatee Rescue, Rehabilitation and Release Program (Rehab Program). This program began in the early 1970s with the goal of assisting injured and distress manatees in the continental United States and the Caribbean. To date the Rehab Program has successfully rescued, medically treated, and released hundreds of injured and distressed manatees.
On July 23, 1997 researchers announced the discovery of a papilloma virus (PV) in Florida manatees undergoing rehabilitation at the Homosassa Springs Wildlife State Park (HSWSP). PV transmissible viruses that are generally species-specific, benign tumors found in numerous mammalian and bird species (Sundberget al. 1995; Sundberg et al. 2000). After the discovery of this virus a quarantine was implemented in 1998 at the facility prohibiting any direct contact between captive manatees housed in the facility and with wild manatees just outside the exclosure fence.
HSWSP, in collaboration with Dr. Greg Bossart and colleagues, began to monitor the infected animals noting lesion numbers, size, location and overall health. In 1999 several biopsies were taken from wild captive manatees and tested for PV. These samples did not indicate the presence of PV, however, these data were based on bovine PV screens, which at the time, was the most advanced technology to test for the virus.
In 2003 researchers successfully sequenced the entire manatee papilloma virus, and designated this virus as TmPV-1 (Rector et al. 2004), the first virus isolated for the Order Sirenia. This research suggested that TmPV-1 was not transmitted to manatees, but rather co-evolved with the species and was present in a latent form in manatee skin. The separation of virus-like particles was also completed allowing for the development of a sensitive specific detection of the organism and a PV vaccine. In 2004 a novel ELISA blood test was also developed to determine exposure to TmPV-1 in manatees; a seroprevalence study was then initiated by Dr. Greg Bossart and colleagues from the James Graham Brown Cancer Center in Louisville, Kentucky. Subsequently, in 2005 archived samples were tested for serum sensitivity to antibody titers for TmPV-1 using the ELISA. Both wild and captive manatees (n = 21 and 20 respectively) from Florida were screened, as well as 23 samples from manatees collected in Mexico. Results demonstrated positive titers for four captive manatees known to have had TmPV-1; however, free-ranging animals showed no titer for TmPV-1.
In the winter of 1998, biologists from the US Geological Survey Sirenia Project (USGS) began collecting manatee skin samples from Homosassa and Crystal Rivers as part of a preliminary study to investigate for the presence of PV in wild manatees. Samples were opportunistically collected through 2003, then subject to DNA extraction and analyzed using polymerase chain reaction (PCR) amplification. Results from this study (Woodroof et al. 2003, Woodruff et al. 2005) supported the presence of PV in six wild manatee samples collected in the winter of 2003. Subsequently, concerns were raised regarding the integrity of the laboratory and possible contamination of the samples collected. An internal review determined the research and its findings were valid, however, concerns and doubts were still expressed within the manatee research and management community, prohibiting the necessary confidence to support a change in management practices or lifting the existing quarantine.
In the fall of 2003 the Service discovered manatees at Sea World San Diego possessed lesions associated with PV. Following this discovery, the Service was also informed about a previously PV infected manatee at Sea World Orlando (SWF). This animal had been housed with many other captive manatees that subsequently were released or transferred to other holding facilities. This new information resulted in an immediate quarantine for both Sea World facilities.
A series of meetings were organized in the spring of 2004 with manatee veterinarians, biologists, caregivers and managers to address the issue of PV in the captive manatee population. An outside panel of disease experts was also convened (Attachment #1) to advise the Service on the best approach for research and management actions to address manatee PV. Unanimous recommendations included: (1) the development of an ELISA screen for both the captive and wild populations; (2) the initiation of an epidemiology study to determine prevalence of PV in the wild; (3) the standardization and continued surveillance for PV in the wild population; (4) the creation of a management plan based on scientific findings of the ELISA test and (5) the prohibition on releasing infected manatees with "active" lesions caused by PV. The Service was also advised to limit the release of “exposed” animals to only the Homosassa River area; however, the Service took a conservative approach and decided not to release “exposed” manatees until it was scientifically proven that PV did exist in free-ranging manatees.
In the winter of 2005-06 USGS biologists, in coordination with the Service, initiated an epidemiology study in the Crystal River/Homosassa Springs region to determine the prevalence of PV in the wild manatee population and investigate the health of animals with suspicious lesions through the change of seasons. To date, the study has been conducted for three field seasons with a total of 37 manatees (24-males, 13-females) captured and examined. Although lesions have occasionally been observed, no validated evidence of PV lesions have been determined using the latest gold standard for testing (i.e., immunohistochemistry, PCR, and general histology).
Since the discovery of PV, Dr. Bossart, Dr. Jensen and colleagues continued to investigate TmPV-1. A cyclical nature of the lesions on the captive manatee population was eventually observed (similar to that observed by field biologists from suspect lesions on wild manatees), indicating the probability of immune compromise and activation of a latent virus infection, as seen in other species infected with PV (Jensen 2008 pers. comm.). This collaboration continued with vaccine trials in 2006 on horses to ascertain the efficacy of the manatee vaccine. Results from the trials indicated a positive immune response and no adverse reactions. Due to permitting and financial constraints, this collaborative work that was intended to test the vaccine and validate the ELISA on captive manatees known to possess TmPV-1 was not completed. Later discussions with clinical veterinarians, researchers and managers concluded a limited applicability of the vaccine, as it was not feasible both financially and logistically to consider vaccinating large numbers of wild manatees.
In the spring of 2008, a recommendation was made to the Service to use existing ELISA methodology to determine the existence of PV in free-ranging manatees. This recommendation resulted in a joint effort among partners within the Rehab Program and the James Graham Brown Cancer Center. Fresh samples were collected from all captive manatees (held in captivity for > 1 month). Additionally, archived samples were obtained from wild manatees in all four designated management units in Florida (i.e., St. Johns River area, Atlantic coast, Northwest region and Southwest region) and from wild manatees in Belize. Drs. Jensen, Ghim, Dona and colleagues used the same ELISA that was previously conducted on captive manatees. Results from the study at the most conservative levels (below that used by Bossart in the 2005 study), revealed free-ranging manatees have been exposed to PV (Dona et al. in review). Additionally, this work supported the established theories that PV co-evolved with the species and all manatees possess a latent form PV which, under certain conditions where a co-factor is present, can become active and eventually non-lethal lesions are presented.
The research from Dona and colleagues resulted in letters to the Service supporting the release of previously infected or “exposed” manatees, pending certain conditions are met; these letters are presented in Attachment 2 of this memo.
Service Position
Given the scientific evidence presented and recommendations from the expert panel, the Service now supports the release of captive manatees that are free of PV lesions, and have been free from lesions or any contact with animals possessing lesions for at least six months.
Our position is based on the following factors: (1) The species-specific nature of PV’s which eliminates concerns that PV could infect other species in the wild; (2) Research by Drs. Jensen and Bossart which supports the theory that TmPV-1 is a subclinical infection that manatees have possessed for millions of years and has co-evolved with species; (3) The recent findings by Dona et al. that prove manatees in the wild are exposed to PV; (4) No manatee has been rescued with a known active PV lesion (n > 900, USFWS unpublished data); and (5) The benign nature of many PV lesions, supported by the fact that no manatee has been known to die as a result of PV (n = 6, 868, FWC unpublished data from April 1974 through September 2008).
Current evidence suggests that PV does not pose a threat to the manatee population; however, the Service will continue to support research to enhance our understanding of this virus. It is believed that wild, healthy manatees have the ability to resolve PV on their own. Monitoring of both the captive and wild populations will continue to ensure that any changes within the wild manatee population are promptly addressed and evaluated.
Nicole M. Adimey
Relevant References
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Bossart, G. D., R. A. Meisner, S. A. Rommel, S-J. Ghim and A. B. Jenson. 2002b. Pathological features of the Florida manatee cold stress syndrome. Aquatic Mammals 29(1):9-17.
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Last modified January 7, 2009
