# Emergent and Known Honey Bee Pathogens through Passive Surveillance in the Republic of Kosovo
## 4 Discussion  
In the last decade, a reduction in honey bee colonies has been frequently reported around the world [2; 54]. Among the causes for mortality and global threat for honey bee colonies are several pathogens and parasites [55].  
Our study was based on passive surveillance on weak honey bee colonies aiming to determine the occurrence and distribution of known and emergent honey bee pathogens in the Republic of Kosovo. An investigation based on passive surveillance was already carried out by [PERSON] et al. [45] focusing on AFB.  
In all the 59 apiaries tested for _Vairinorpha_ spp., a high percentage of infection (100%) with _V. ceranae_ was found, while no samples tested positive for _V. apis_. These data confirm what has already been reported in Italy [47; 56] and in the neighbouring countries to the Republic of Kosovo, such as Serbia, Croatia, Bosnia-Herzegovina, Montenegro, North Macedonia, and Bulgaria, where _V. ceranae_ dominates in microsporidia infections in honey bees [57; 58; 59; 60; 61]. Furthermore, this finding confirmed the previously reported higher diffusion of _V. ceranae_ in other European countries and worldwide [62; 63; 64; 65]. The presence of _V. ceranae_ infection could reduce honey bee lifespan [7], significantly increase honey bee worker mortality, and could be one stressor responsible for elevated colony losses [66].  
In the Republic of Kosovo, _L. passim_ was only detected in seven of fifty-nine apiaries (11.9%) from four municipalities during the passive surveillance. In the Veneto region (northern Italy), _L. passim_ was detected in almost all of the apiaries analysed with an overall positivity rate of 48.8% in 2020, while an increase was observed in 2021 with an overall value of 62.2% [47]. In Serbia, _L. passim_ was detected during 2007-2015 every year. In the Republic of Kosovo, _C. mellificae_ was never reported, as well as in neighbouring Serbia [67].  
In our study, five honey bee viruses were found (ABPV, CBPV, DWV, BQCV, SBV) and the most frequent were DWV and BQCV with 100% and 92.3% prevalence in the 13 apiaries analysed, respectively. ABPV was detected in nine apiaries (69.2%), SBV in four apiaries (30.8%) from four municipalities, and CBPV in only one apiary (7.7%). No positivity for IAPV and KBV was observed in the investigated apiaries.  
When comparing our research on honey bee viruses with other countries, we found that the same viruses (ABPV, CBPV, DWV, BQCV, and SBV) have also been detected in neighbouring Serbia, Austria, Greece, and other countries [68; 69; 70; 71], whereas KBV was also detected in France [20]. The presence of DWV is often associated with _V. destructor_ infestation, and the role of this mite in viral transmission has already been experimentally demonstrated [72]. It is known that DWV, vectored by the _Varroa_ mite, adversely affects humoral and cellular immune responses and promotes the reproduction of this parasitic mite [27].  
Both BQCV and SBV are not known to be transmitted by _V. destructor_[73]. However, a significantly higher prevalence of BQCV and SBV in colonies infested with _V. destructor_ mites has been detected, hypothesizing the role of _V. destructor_ in their transmission [74]. In our study, considering not only honey bee but also _Varroa_ mite samples, the virus frequency was increased for ABPV (from 69.2% to 84.6%) and CBPV (from 7.7% to 15.4%).  
Furthermore, larvae collected from the brood comb tested for AFB were positive for the _P. larvae_ ERIC I genotype in eight out of nine apiaries. This finding is in line with the results of the passive survey carried out during 2007-2019 that revealed a wide diffusion of AFB of the ERIC I and II genotypes in the country [45], thus suggesting the necessity of applying active disease surveillance strategies. The single positivity detected for EFB suggests that the disease is present in the country but further investigations are needed to understand its true distribution and possible impact on honey bee colonies.