Amphibians of Madagascar have long been threatened by habitat destruction and overexploitation for the pet trade, but a recent report of widespread amphibian chytrid fungus (Batrachochytrium dendrobatidis, hereafter “Bd”) suggests a catastrophic disease event that may cause amphibian decline and extinction is now immediately possible (Bletz et al. 2015).
The agent of disease, Bd, was heretofore believed absent from Madagascar, a global hotspot for amphibian diversity home to over 300 species of frogs found nowhere else on Earth. Although some amphibians have recently been found infected with Bd, no signs of disease (negative effects of infection) have yet been observed.
Bd appears to already have been present in Madagascar for several years (Kolby 2014 a) and it is remarkable that Bd-associated amphibian declines and extinctions have not yet occurred. The recent detection of Bd in Madagascar provides a warning that opportunities for Bd introduction exist and the current opportunity to prevent a disease outbreak is extremely uncommon and time-sensitive. The recent review of all published data from 10 years of Bd surveys in Madagascar (Kolby & Skerratt 2015), suggests that Bd might not yet have been introduced at high enough densities and/or to suitable habitats for the emergence of permanent self-sustaining Bd populations. No viable method of Bd eradication from the environment following its establishment has been demonstrated, thus the need for emergency preventative measures in Madagascar.
It is uncertain exactly how and when Bd arrived in Madagascar, but continued introduction can expose native amphibians to disease strains with greater virulence than those already present. Therefore, any rapid response to protect the amphibians of Madagascar should involve preventative actions to mitigate the risk of additional Bd importation and accelerated spread by human activities. Unfortunately, now nearly two years after the discovery of Bd in Madagascar, little preventative action has been implemented.
International trade provides a pathway for hitchhiking amphibians to carry Bd into Madagascar. Asian toads (Duttaphrynus melanostictus) are believed to have been introduced as stowaways in ocean shipping containers, and are now reproducing and spreading into the mainland from the port city of Toamsina, Madagascar (Kolby 2014 b). These toads can serve as a vehicle ofBd introduction to the country and pose a high risk of exposure to native amphibians as they disperse across the landscape. A program to require careful inspection of incoming ocean cargo and interception of alien amphibians is urgently needed to reduce the number of new animals that escape into Madagascar.
Within Madagascar, amphibians from around the country are collected and sent to centralized wildlife facilities to supply the international wildlife trade. Animals exported from Madagascar have been found infected with Bd (Kolby 2014 a) and the local personnel collecting, transporting, and handling Bd-positive frogs must be made aware of the risk of disease spread. Contaminated shipping boxes, substrates, and carcasses should be exposed to bleach or incineration to neutralize the threat prior to disposal outdoors where these materials can remain infection for weeks to local amphibians. Biosecurity efforts to reduce the spread of Bd are likely to also reduce the spread of ranavirus, an emerging wildlife pathogen that can affect amphibians, reptiles, and fishes. Since we detected both ranavirus and Bd at the same trade facility in Madagascar, co-infection may particularly threaten wild amphibian populations near trade centers that do not employ biosecurity measures (Kolby et al. 2015).
Now is the time to establish a targeted biosecurity response to reduce the risk of an otherwise predicable biodiversity crisis. The aforementioned measures to preempt additional spread of Bd into and within Madagascar by commercial activities are relatively inexpensive and easy to implement, and begin with greater public education and awareness, within Madagascar and internationally. Institutions in Madagascar are becoming poised for triage if disease suddenly emerges, but the future survival of the vast diversity of Madagascar’s amazing amphibians hangs in the balance. We must decide now if we are to mount a vigorous proactive effort to prevent Bd establishment in Madagascar because soon the choice will no longer be ours to make.
By Jonathan Kolby
Bletz MC, Rosa GM, Andreone F, Courtois EA, Schmeller DS, Rabibisoa NHC, et al. (2015) Widespread presence of the pathogenic fungus Batrachochytrium dendrobatidis in wild amphibian communities in Madagascar. Sci. Rep. 5: Article No. 8633.
Kolby JE. (2014 a) Presence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in native amphibians exported from Madagascar. PLOS ONE 9(3): e89660. doi:10.1371/journal.pone.0089660
Kolby JE. (2014 b) Stop Madagascar’s toad invasion now. Nature Corresp. 509: 563.
Kolby JE, Skerratt LF (2015) Amphibian Chytrid Fungus in Madagascar neither Shows Widespread Presence nor Signs of Certain Establishment.PLoS ONE 10(10): e0139172. doi:10.1371/journal.pone.0139172
Kolby JE, Smith KM, Ramirez SD, Rabemananjara F, Pessier AP, Brunner JL, et al. (2015) Rapid Response to Evaluate the Presence of Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) and Ranavirus in Wild Amphibian Populations in Madagascar. PLoS ONE 10(6): e0125330. doi:10.1371/journal.pone.