Epidemiology
Epidemiology differs among the countries in which it has been reported, and is dependent upon temperature and rainfall patterns, and the subsequent multiplication of the fly vectors.
In Germany, the verminous nodules start in May and June, 2 to 4 weeks after the beginning of pasture feeding. They heal spontaneously in October and November.
In Morocco, the disease is observed in years when heavy rainfalls occur in March and April. Numerous cases are then observed in April and May, in the immediate surroundings of the ponds. Some cases will heal spontaneously, but some others lead to wide subcutaneous lesions which require a veterinary treatment. The repartition and gravity of the skin lesions suggests that the causative agent may be slightly different from the one observed in Western Europe.
Read more about this topic: Verminous Haemorrhagic Dermatitis (cattle)