Nosema ceranae causes cellular immunosuppression and interacts with thiamethoxam to increase mortality in the stingless bee Melipona colimana

Abstract

The microsporidian parasite Nosema ceranae and neonicotinoid insecticides affect the health of honey bees (Apis mellifera). However, there is limited information about the effect of these stressors on other pollinators such as stingless bees (Hymenoptera: Meliponini). We examined the separate and combined effects of N. ceranae and the neonicotinoid thiamethoxam at field-exposure levels on the survivorship and cellular immunity (hemocyte concentration) of the stingless bee Melipona colimana. Newly-emerged bees were subjected to four treatments provided in sucrose syrup: N. ceranae spores, thiamethoxam, thiamethoxam and N. ceranae, and control (bees receiving only syrup). N. ceranae developed infections of > 467,000 spores/bee in the group treated with spores only. However, in the bees subjected to both stressors, infections were < 143,000 spores/bee, likely due to an inhibitory effect of thiamethoxam on the microsporidium. N. ceranae infections did not affect bee survivorship, but thiamethoxam plus N. ceranae significantly increased mortality. Hemocyte counts were significantly lower in N. ceranae infected-bees than in the other treatments. These results suggest that N. ceranae may infect, proliferate and cause cellular immunosuppression in stingless bees, that exposure to sublethal thiamethoxam concentrations is toxic to M. colimana when infected with N. ceranae, and that thiamethoxam restrains N. ceranae proliferation. These findings have implications on pollinators’ conservation.

Deteriorating microbiomes in agriculture - the unintended effects of pesticides on microbial life

“…That is, the persistence of host-adapted microbial communities is a bidirectional process, and thus this may functionally explain how immune dysregulation by neonicotinoids could (indirectly) result in a loss of microbial diversity over time under realistic scenarios of chronic exposure. It is also foreseeable how these effects could exacerbate the loss of microbial diversity during concurrent exposure to chemicals that do possess antimicrobial capacities, such is the case for antibiotics [85] and fungicides [86] -the latter of which is consistent with results showing a near doubling of the apparent honey bee mortality risk over a four-month period during neonicotinoid coexposure [78] . Collectively, the current literature suggests that the microbiome-disrupting effects of pesticides are not always as clear as direct inhibition, and in the case of neonicotinoids in bees, appear to be mediated indirectly via host immune dysregulation [Figure 2C], and at concentrations not otherwise directly toxic to bee physiology.…”

La miel de abejas sin aguijón: una medicina diferente

“…Otro enemigo descrito es la abeja ladrona, abeja limón o Lestrimelitta sp., llamada así por el fuerte olor que emanan las abejas obreras al momento del ataque y la colonización del nido [9]. Pero no hace mucho, en el 2017 evidenciaron la presencia de un hongo microsporidio del género Nosema en las abejas sin aguijón [20], [21].…”

Honeybee visitation to shared flowers increases Vairimorpha ceranae prevalence in bumblebees

“…Symptoms are generally assumed to be the same for wild bees, but data on this are limited aside from a few reports that V. ceranae may cause reduced survival, learning impairment, lower sucrose sensitivity, and cellular immunosuppression in bumblebees and stingless bees (Graystock et al, 2013;Macías-Macías et al, 2020;Piiroinen & Goulson, 2016). Furthermore, V. ceranae infections suppress the pollinator immune response, which can lead to coinfection with other pathogens or parasites and an increased likelihood of mortality (Antúnez et al, 2009).…”