protein VP2 allowed it to cross the species barrier, and dogs, unlike cats, had no resistance to the disease. Canine distemper virus is closely related to measles virus and is the most important viral disease of dogs. The disease (which was first described in 1760, by Edward Jenner, the pioneer of smallpox vaccination, is highly contagious, but is well controlled by vaccination. In the 1990s, thousands of African lions died from the infection, which they contracted from feral dogs and hyenas. Marine mammals are susceptible to viral infections. In 1988 and 2002, thousands of harbor seals were killed in Europe by the measles-like phocine distemper virus. Large outbreaks of the disease were recorded among the seal populations of Lake Baikal and along the shores of the Baltic and North Sea. The infection resembled canine distemper; the animals died within two weeks of respiratory distress and many aborted pups were seen. Many other viruses, including caliciviruses, herpesviruses, adenoviruses and parvoviruses, circulate in marine mammal populations. Fish too have their viruses. They are particularly prone to infections with rhabdoviruses, which are distinct from, but related to rabies virus. At least nine types of rhabdovirus cause economically important diseases in species including salmon, pike, perch, sea bass, carp and cod. The symptoms include anaemia, bleeding, lethargy and a mortality rate that is affected by the temperature of the water. In hatcheries the diseases are often controlled by increasing the temperature to 15–18 °C. Like all vertebrates, fish suffer from herpes viruses. These ancient viruses have co-evolved with their hosts and are highly species-specific. In fish, they cause cancerous tumours and non-cancerous growths called hyperplasia. Invertebrates Arthropods is the largest group of animals and has shown to be a major reservoir of different viruses, both insect-specific viruses (ISV) and viruses that can infect both vertebrates and invertebrates, more known as arthropod-borne viruses (arboviruses). Insect-specific viruses are, as the name reveals, characterised by their incapacity to infect vertebrates. This can be assessed through, viral inoculation of mammalian, avian, or amphibian cell lines. The first (ISV) was discovered over 40 years ago by Stollar and Thomas. It was isolated from an Aedes aegypti cell culture where a large number of syncytia were observed and the virus was named cell fusing agent virus (CFAV). Further, when inoculated on different vertebrate cell lines no cytopathic effect (CPE) could be observed and the virus could not be re-isolated, suggesting