First record of Apicystis sp. (Apicomplexa: Neogregarinorida) in Moroccan honey bees

Primer registro de Apicystis sp. (Apicomplexa: Neogregarinorida) en abejas melíferas marroquíes

Esta obra está bajo una Licencia Creative Commons Atribución 4.0 Internacional.

Hymenopteran pollinators, such as honey bees (Apis mellifera L.) and bumble bees (Bombus spp.) (Apidae), are key species in the process of angiosperm pollination, ensuring the well-being of ecosystems, the preservation of biodiversity, and food production (Gallai et al., 2009; Schulp et al., 2014; Mouillard-Lample et al., 2023). The population dynamics of these insects is permanently threatened by several, external factors, of which entomopathogens are key. These infectious agents are mainly found in honey bees sampled in commercial apiaries, but not in bumble bees or other bees worldwide, where understanding of parasitic diseases is still in its early stages (Goulson et al., 2015; Proesmans et al., 2021).

Honey bees can be affected, besides viral and bacterial agents (Pasho et al., 2021), by other unicellular parasites such as Microsporidia (Vairimorpha apis (Zander) and V. ceranae^[1]Fries et al.) and protists [Crithidia mellificae (Langridge & McGhee), Lotmaria passim Schwarz (Euglenozoa) and Malphigamoeba mellificae (Prell) (Amoebozoa)]. Both V. apis and V. ceranae cause the disease called Nosemosis (Mazur & Gajda, 2022; Parrella et al., 2024), whereas the protists which may (or not) occur with a relevant health impact (Schwarz et al., 2015; Shäffer et al., 2022). In the last 10-15 years, another protozoan that normally infects bumble bees, the neogregarine Apicystis bombi Liu et al. (Apicomplexa: Neogregarinorida) was registered in honey bees from South America, North America, Europe, Asia and Africa (reviewed by Plischuk & Lange, 2024). More recently, a new species of Apicystis Lipa & Triggiani (A. cryptica Schoonvaere et al.) was isolated from Bombus pascuorum Scopoli in Belgium, being this bumble bee, its only known host so far (Schoonvaere et al., 2020). Both Apicystis species have been detected in the adipose tissue of their hosts, where they disrupt tissue integrity and lead to subsequent nutritional imbalances. The extent to which A. bombi displays comparable virulence in other hosts - such as honey bees or carpenter bees, in which it was also found - remains unclear (Chantawannakul et al., 2016; Plischuk et al., 2023; Plischuk & Lange, 2024 and references therein).

⁽¹⁾Formerly Nosema apis and Nosema ceranae, resp. (Tokarev et al., 2020 but also see Bartolomé et al., 2024).

Figure 1.
Souss-Massa region, Morocco.

Yellow stars indicate Apicystis-positive A. melliferasahariensis apiaries. Pink stars indicate Apicystis-positive A. melliferaintermissa apiaries.

In this research, 206 samples of adult honey bee workers were collected from 206 apiaries across the Souss-Massa region, southwestern Morocco (30°5'13"N; 8°27'38"W; Fig. 1). Each sample consisted of a pool of ~80 bees taken from the same apiary. Bees were identified and preserved in 70 % ethanol flasks until analyses. Note that the two subspecies sampled are easily distinguishable: A. mellifera sahariensis (Baldensperger) (“Saharan honey bee”) is more yellowish than A. mellifera intermissa von Buttel-Reepen(“Tellian honey bee”). The analyses were conducted using a microscopic screening of homogenized bee metasomes (PCM, 40x – 100x). Morphological characters described by Lipa & Triggiani (1996), and Plischuk & Lange (2009) were used to recognize the Apicystis oocysts (Fig. 2). Presence of Apicystis was observed in 17 samples, meaning a total prevalence of 8.25 % in that study area. The cases concerned five samples of A. mellifera sahariensis (n= 39) and twelve samples of A. mellifera intermissa (n= 167).

Figure 2.
Apicystis sp. oocysts.

a. Mature oocyst (left) and a spore of Varimorpha sp. (right). b. Oocysts showing sporozoites inside.

These findings allow us to report the occurrence of Apicystis sp. in Moroccan honey bees for the first time. Furthermore, this record constitutes the second report from Africa after that of Menail et al. (2016), who reported the presence of A. bombi in A. mellifera intermissa adults (prevalence= 2.27 %; n= 44) collected in the Annaba region, Algeria (ca. 1,600 km from Souss-Massa region).

This parasite appears to infect bumble bees as its natural hosts; however, in the last decade this apparent specificity has been expanded and it should not be ruled out that it could also be harmful in certain alternative hosts such as honey bees or carpenter bees (Xylocopa spp.), although the pathogenicity of Apicystis in these non-Bombus species has not been confirmed (Plischuk et al., 2023; Plischuk & Lange, 2024). In this case, unlike what was reported by Plischuk et al. (2011), a large percentage of the observed oocysts using phase-contrast microscopy showed refringence, a fact that could indicate viability. In Poland, Schulz et al. (2019) found oocysts in both hemocoel and ventriculus of A. mellifera workers, but not in the adipose tissue. Unfortunately, since Moroccan bees were analyzed by homogenization, the tissue in which these oocysts were lodged could not be determined.

As in South America (see Plischuk & Lange, 2024), the presence of this neogregarine in Souss-Massa, geographically far from other reports, is another interesting case to analyze. Considering that three (or four) species of Bombus [B. lapidarius (L.), B. ruderatus (Fabricius), B. terrestris (L.), and probably B. mocsaryi Kriechbaumer (Rasmont & Iserbyt, 2010-2013)] have been recorded in Morocco, Apicystis could be also parasitizing individuals of these species, or another pollinator species, but reports of this are absent in the entire region. This could be due to the lack of additional surveys conducted throughout the Maghreb region looking for possible hosts, that could complement the findings of Menail et al. (2016) in Northeastern Algeria and the present report. Given this lack of information, the implementation of monitoring programs to establish the occurrence of both pathogens and parasites in pollinators, remains fundamental and should be initiated as soon as possible in order to protect native bee populations.

Regarding A. cryptica, even though it has only been found in bumble bees from Belgium, both Apicystis species mentioned are almost indistinguishable based on their morphological characters; therefore, the present work should be furthered using molecular techniques in order to accurately identify the species present in Morocco. However, considering the possible impacts of these pathogens on honey bee health, the present findings are relevant and need to be communicated. Apiculture in the Maghreb region, particularly in Morocco, which ranks the highest in biodiversity across the Mediterranean basin, plays a vital role not only from an ecological point of view but also from a food production, and therefore requires significant attention. In this context, beekeepers should consider potential pathogens, including new emerging diseases that could threat this key sector, not only in the Morocco, but also in similar ecoregions on both shores of the Mediterranean: North Africa and Europe. Authors hope that this report adds another piece in the puzzle of honey bee health-related data worldwide and be considered for further regional research.

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