The distribution and population dynamics of the honey bee pathogens Crithidia mellificae and Lotmaria passim in New Zealand
The honey bee Apis mellifera is experiencing colony losses across the world, this is not the first time in history colony losses have been reported. New molecular detection methods such as real-time PCR allow the detection and analysis of pathogens present in colonies, quickly and reliably. Of the pathogens that the honey bee is host to, trypanosomes are one of the least understood and trypanosome interactions within the honey bee host remain largely unknown. Using the bumble bee as a model for this host-parasite relationship. The trypanosome C. bombi is known to cause a reduced ability to gain nutrients from food and an overall decrease in efficiency of queens in founding colonies in spring. These negative correlations are significant enough in the bumble bee to warrant investigation into trypanosomes in the honey bee. The trypanosome C. mellificae was first described in the honey bee in 1967. A screening study in 2009 included a test for and detected the trypanosome in modern honey bee samples. In 2013 C. mellificae was identified as a contributory factor to overwintering colony losses when co-infected with N. ceranae. Following studies detected trypanosomes and led to the characterisation of a new species, L. passim in 2013. Lotmaria passim was first detected in New Zealand in 2014 however no subsequent studies had been undertaken to identify the distribution and dynamics of trypanosomes in New Zealand honey bee colonies. My goal in this study was to identify the presence of trypanosomes in New Zealand. In an overview study of 47 honey bee colonies from across New Zealand, 46 were positive for the L. passim species. Identified by sequencing of the GAPDH gene. A yearlong study of 15 colonies revealed that the infection rate of L. passim was consistent throughout the year and very low genetic variation was detected. Lotmaria passim was detected in all parts of New Zealand sampled in this study and often in high levels. A positive correlation was detected when L. passim was present in addition to N. apis. There was no detection of C. mellificae in my study. The lack of detection of C. mellificae may suggest that the species is not present, or that it is in such low levels it cannot yet be detected. In parallel to this trypanosome study two Nosema spp. and DWV were also examined. Nosema apis was found to be more prevalent than N. ceranae, which was not present in any South Island samples. A strong positive correlation was detected between the two Nosema spp. DWV showed a high level of variation likely a reflection of differing Varroa management practices in apiaries in this study. This study of trypanosomes is the first of its kind in New Zealand identifying the presence and population dynamics of L. passim. This in conjunction with data on Nosema spp. and DWV will be of value to the New Zealand apiculture industry and contribute to global honey bee health studies.