Parasites plague honeybees all over the world. The Varroa destructor mite has been one of the biggest problems in North America and Europe for the European honeybee (Apis mellifera) and these mites and their impact on honeybees have been studied for many years.
A different variety of mites has been plaguing bees in tropical and subtropical Asia for many decades. These are in the genus Tropilaelaps, and there are four currently known species: clareae, koenigerum, mercedesae and thaii. These were identified in 1961 as parasites of Apis dorsata and Apis laboriosa bees, which are mostly found in China, Vietnam, Thailand, and Philippines as well as India, Sri Lanka, Pakistan, and Afghanistan.
Over the past few decades, these mites have been moving beyond their native range and have invaded European honeybee hives in regions where their habitats overlap. They feed on developing bees and kill them and are considered a major economic threat to the beekeeping industry. In Europe and the USA, authorities are preparing for the inevitable invasive threat from this pest.
This unrelated 7:08-minute video by Inside The Hive gives an in-depth insight into Tropilaelaps mites.
So far, only two of the mite species, T. clareae and T. mercedesae—are known to infest Apis mellifera hives. The other two species have only impacted A. dorsata and A. laboriosa hives.
A precise identification method for these mites that specifically invade A. mellifera hives is needed. Those already in place consist of cruder techniques like the “bump” method, which can detect the presence of mites but does not identify the species, or morphological examination, which achieves species identification but is a more involved process and requires mite examination expertise.
Asian honeybees have developed quite effective defenses to reduce severe infestations of Tropilaelaps, but European honeybees lack these defenses.
Scientists at the honey bee pathology unit at ANSES, the French Agency for Food, Environmental and Occupational Health & Safety decided to seek a rapid, precise ID method with the polymerase chain reaction (PCR). This is a trusted method that uses DNA sequence for precise identification of organisms. By using high-resolution melting analysis (HRM) on the PCR-amplified DNA they were able to find a unique molecular signature for each mite species. This PCR/HRM test easily and quickly identified each of the four mite species.
These results are the first to show a PCR/HRM test for bee mite genome. The report was published in January in the Journal of Economic Entomology and you can read more about the science of this testing method by clicking on this link that takes you to the report.
Their method showed four distinct melt curves for the four mite species. The specific test did not produce results when used against other mite species, including Varroa destructor.
The authors wrote in their report that Tropilaelaps could do more damage and be an even greater threat to Apis mellifera colonies than Varroa destructor mite.
The parasite T. mercedesae is widespread and this parasite could become an important pest in the future. The researchers say ongoing surveillance of Apis mellifera is essential. Given climate change issues and importations, Tropilaelaps mites are an important emerging threat in countries that are currently free of these parasites.