*Case Report* **A Case Report of Chronic Stress in Honey Bee Colonies Induced by Pathogens and Acaricide Residues**

**Elena Alonso-Prados 1, Amelia-Virginia González-Porto 2, José Luis Bernal 3, José Bernal 3, Raquel Martín-Hernández 4,5 and Mariano Higes 5,\***


**Abstract:** In this case report, we analyze the possible causes of the poor health status of a professional *Apis mellifera iberiensis* apiary located in Gajanejos (Guadalajara, Spain). Several factors that potentially favor colony collapse were identified, including *Nosema ceranae* infection, alone or in combination with other factors (e.g., BQCV and DWV infection), and the accumulation of acaricides commonly used to control *Varroa destructor* in the beebread (coumaphos and tau-fluvalinate). Based on the levels of residues, the average toxic unit estimated for the apiary suggests a possible increase in vulnerability to infection by *N. ceranae* due to the presence of high levels of acaricides and the unusual climatic conditions of the year of the collapse event. These data highlight the importance of evaluating these factors in future monitoring programs, as well as the need to adopt adequate preventive measures as part of national and international welfare programs aimed at guaranteeing the health and fitness of bees.

**Keywords:** honey bees; *Apis mellifera*; acaricides; pesticides; toxic unit; *Varroa destructor*; *Nosema ceranae*; bee viruses; tau-fluvalinate; coumaphos
