Batrachochytrium dendrobatidis (hereinafter Bd), a fungus that causes a deadly amphibian infection, decimates their populations around the world. With the exception of Antarctica, this mold is widespread on all continents. In Asia, the largest continent, however, its occurrence has rarely been studied, so a group of scientists, including experts from the Faculty of Forestry and Wood Technology, travelled to the Far East of Russia for samples.
Chytridiomycosis, a serious infectious disease caused by this fungus, was first detected in the late 20th century. Visual symptoms are obvious. Infected individuals suffer from keratinization of the skin, peeling or purulent discharge on the skin, muscles or eyes. These morphological features are accompanied by motor impairment, rigidity in an unnatural position, lethargy, and loss of natural reflexes.
Mass mortality of populations has been observed in Australia, America and Europe. Current Asian surveys confirm the presence of Bd in China, Japan, Indonesia, Malaysia, South Korea, Kyrgyzstan, Laos, but also in the Philippines, Sri Lanka and Vietnam. However, due to the vast size of the Asian continent, many parts remain unexplored, and this research, conducted in the Russian Far East near Vladivostok, was one of the first attempts within the Russian Federation.
The research took place in the spring months in two consecutive years at seven sites. The sampling site was mostly small ponds and estuaries. The most challenging factor was the capture of amphibians, which were trapped in the water in a net attached to long handles or directly on land into the hands. The actual collection of material for analysis was performed by smearing the skin with cleaning sticks with cotton wool, which we all know well. High hygiene measures were in place here. As the risk of infection was spreading, rubber gloves were a necessary part of the whole process. Selected individuals were photographed after the smear and returned to the place of capture. A total of 180 samples of three amphibian species were analysed. Specifically, these were frogs from the Ranidae and Bufonidae families and salamanders from the Hynobiidae family.
The samples were processed according to standard procedures using the so-called hydrolysis TaqMan probe based on the method developed in 1983 used to create many millions of copies of the DNA fragment. It is so sensitive that it can detect even a single DNA molecule from a sample.
The tests turned out as expected. As no suspicious deaths were observed in North Asia, such as in America or Europe, the team partially anticipated the results. The presence of mold was not confirmed in any of the studied samples, i.e. the overall prevalence * was zero. Compared to other positive research results (prevalence up to 8%) in Japan or China, for example, it has been shown that the incidence of Bd in Asia is not universal and that there are still areas without these pathogens.
The scientific team emphasized the importance of research. In contrast to sites after disease gradation, it is possible to observe in these demonstrably unaffected localities what factors will influence the possible origin and spread of this pathogen. It follows that it is essential to continue to monitor and protect these so far healthy populations.
* the share of the number of individuals suffering from a given disease and the number of all individuals in the monitored population related to a certain point in time
Civiš, P., Vojar, J., Baláž, V., Kohoutka, A., Ulbrichová, I., Dvořák, V.: Sampling for Batrachochytrium dendrobatidis in Russia. Herpetological Journal, 2013, roč. 23, č. 1, s. 55–58. ISSN: 0268-0130.
Ing. Iva Ulbrichová, Ph.D.
In 1996 she graduated in Horticulture at the CULS Faculty of Agriculture and in 2002 she obtained a doctoral degree at the Faculty of Forestry in the field of Anatomy and Physiology of Forest Trees. Currently she works at the Department of Forest Ecology of the Faculty of Forestry and Wood Sciences.
Prepared by: Jakub Málek