MOLECULAR DETECTION OF EQUID HERPESVIRUS TYPE 2 (EHV-2) AND TYPE 5 (EHV-5) IN 2 BRONCHOALVEOLAR LAVAGE FLUID FROM ASYMPTOMATIC THOROUGHBRED HORSES IN 3 SOUTHERN BRAZIL 4

Background: Respiratory conditions are the leading cause of training disruption in racing horses. 28 Molecular approaches to diagnose respiratory viruses have provided an opportunity for early and subclinical pathogen detection, particularly in samples from the upper respiratory tract. 30 Gammaherpesvius (EHV-2 and EHV-5) have variable presentations in horses. However, the infection 31 can be asymptomatic and act as a co-factor for the development of other diseases. In this descriptive 32 observational study, 10 healthy, young horses at regular training in Southern Brazil underwent clinical 33 examination, videoendoscopy of the respiratory system, cytological evaluation of TA (tracheal aspirate) 34 and BALF (bronchoalveolar lavage fluid), along with qPCR, in order to evaluate the presence of EHV- 35 2 and EHV-5 in lower respiratory tract samples and compare with correspondent cytological and 36 endoscopical findings. Results: At least one abnormality per horse during endoscopy examination was observed, including, 38 but not limited to, mucous secretion in the airways and pharyngeal lymphoid hyperplasia. The presence 39 of EHV-2 and EHV-5 was detected by qPCR in three out of ten animals. One horse was positive for 40 EHV-2 alone, one for EHV-5 alone, and one was positive for both viruses. No videoendoscopic finding 41 correlated with each other neither predicts gammaherpesvirus status (positive or negative test). 42 Additionally, there was no relationship between the percentage of cells in both TA and BALF and the 43 probability to test positive for herpesvirus. 44 Conclusions: To the authors’ knowledge, this is the first molecular detection of EHV-2 and 5 in 45 Brazilian Thoroughbred horses. These findings may provide new insights into the epidemiological 46 situation of EHV-2 and 5 in Brazilian athletic young horses, evidencing the importance of the molecular 47 investigation, early detection, prevention of respiratory diseases. positivity for gammaherpesvirus based on the percentage of cells present in BALF TA. correlation among videoendoscopic findings and positivity gammaherpesvirus Spearman’s Prism 8.0.2,


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Five out of nine identified species of equid herpesviruses infect the domestic horse. Two belong 60 to the subfamily Gammaherpesvirinae (EHV-2 and EHV-5) and three to the subfamily 61 Alphaherpesvirinae (EHV-1, EHV-3, and EHV-4). Except for EHV-3, which is a venereal pathogen, all 62 herpesviruses cause upper or lower respiratory diseases in horses and are endemic worldwide (4-6).

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The EHV-2 and EHV-5 have a variable presentation, from pharyngitis, lymphadenomegaly, fever, and 64 anorexia to pneumonia or multinodular pulmonary fibrosis (EMPF). However, like other herpesviruses, 65 the infection can lead to no clinical signs and latency, or act as a co-factor for the development of other 66 diseases. The full pathogenic potential of gammaherpesviruses remains unclear (7-9).

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(13, 14)), although three animals (horses 1, 2, and 5) had only mildly increased numbers of 118 lymphocytes. Seven horses had more neutrophils in their TA than in their BALF. However, only two 119 horses reached the cutoff for neutrophilic inflammation (>20%) (16); these two animals were positive 120 for herpesvirus. One horse had a lymphocytic inflammation (lymphocyte was the predominant cell type).

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There is no relationship between the percentage of cells in both TA and BALF and the probability to 122 test positive for herpesvirus. However, the percentage of neutrophils in TA showed a statistical trend (p 123 = 0.0527).

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The most consistent videoendoscopic finding in all animals was PLH, which is significantly

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Electronics Co., Shenzhen Shi, China) followed by a manual differential count. Total plasma protein 208 and fibrinogen, using the heat-precipitation method, were determined by refractometry.

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The animals underwent a one-hour training approximately 24 hours before blood collection,