Description of the Clinical Findings Associated With the Epizootic Hemorrhagic Disease in Cattle From Northwestern Spain During the Emergence

Abstract

Epizootic hemorrhagic disease (EHD) is an emerging disease in Europe since it was first introduced in 2022 in Italy, Spain, and Portugal. The disease is traditionally considered less severe in cattle, but outbreaks have appeared with increasing frequency in the last decades. The outbreak in Spain coursed with numerous cattle farms reporting clinical disease. Our aim in this study was to evaluate the incidence of clinical disease in cattle farms from NW Spain and describe the clinical signs and their frequency. We investigated 29 cattle farms that reported EHD and estimated an incidence of farms with clinical signs of 6.2% (n=467) in the study area (range: 2.3%-33.3%). The mean incidence of clinical signs, mortality, and lethality rates were 8.9%, 1.7%, and 23.0%, respectively. Interestingly, mortality and lethality were significantly higher in dairy cattle than in beef (OR of 3.0 and 4.4, respectively). Oral lesions, dysphagia, and hoof problems were common clinical signs found in the study. Among all, the presence of tongue edema, dehydration, and dyspnea was associated with higher lethality rates. These results highlight a significant impact of EHD during the emergency. In fact, it must be noted that our data are based on passive surveillance, so true incidences are likely to be higher. The clinical signs and epidemiologic characteristics reported in this paper may contribute to understanding the clinical implications of the disease in cattle and help anticipate the effects of EHD virus (EHDV) introduction into naïve regions.

Keywords: EHD; clinical signs; oral lesions; ruminants; vector-borne.

Figure 1

(a) Spatial distribution and temporality of EHD confirmed cases in NW Spain by the end of 2023; (b) spatial distribution of the sampled farms (n=29) and incidence of clinical signs by municipality; (c) temporality of the beginning of cases in the sampled farms; (d) distribution of the municipality-level incidence of clinical signs.

Figure 2

(a) Percentage of farms that presented clinical signs according to their farm type and severity: NM-SD no mortality and short-duration; M-SD: mortality and short-duration; HM-LD: high mortality and long duration; NLM-LD: no or low mortality and long duration; (b) percentage of farms that presented animals with clinical signs in each age group.

Figure 3

(a) Percentage of farms that declared each clinical sign in each category of frequency; (b) percentage of farms that presented each clinical sign by farm type.

Figure 4

(a) Animal showing erosions and ulcers in mouth along with hypersalivation; (b) reddening and ulcers in the muzzle, tongue edema with tongue protruded; (c) coronary band injury and shedding of the hoof capsule.