What are the main differences between RHDV and RHDV2?
The emergence of a new RHDV (RHDV2) in 2010 partially changed the epidemiology of this disease. The lack of prior protective immunity allowed the disease to spread rapidly across Europe causing high mortality in both domestic and wild rabbit populations.
| RHDV, GI.1 or classical strain | RHDV2, GI.2 or variant strain | |
|---|---|---|
| First reported | 1984 in China | 2010 in France |
| Target | Adult rabbits* (Oryctolagus cuniculus) | Rabbits > 7 days of age (Oryctolagus cuniculus), cottontail (Sylvilagus) and some hares: Sardinian cape hare (L. capensis var mediterraneus), the Italian hare (L. corsicanus), the brown hare (L. europaeus) and mountain hare (L. timidus) |
| Incubation period | 1 – 3 days | |
| Mortality | 80 – 90% | 50 – 90% |
| Clinical signs | Similar | |
If we compare the affected species, RHDV2 has been able to expand the target species to cause the disease not only in rabbits, but also in other leporidae. As it spreads into new regions, new affected species are discovered which were previously unknown.
Although the severity of the disease may differ between RHDV and RHDV2, it is not possible to differentiate the type of strain without a laboratory diagnosis. For this reason, viral detection techniques can be performed, such as RT-PCR. This molecular method allows rapid laboratory results to be obtained with high sensitivity. The sample of choice is the liver, since it is the main organ where the virus replicates.
The incubation period of RHD can vary from 1 to 3 days. Hyperacute cases are usually characterized by sudden death without any previous clinical signs. Sometimes infected animals have a high fever (>40ºC). However, due to the rapid progression of the disease, it is often not clinically detectable.
Subclinical chronic cases are characterized by generalized jaundice, weight loss, and lethargy.
According to the cited bibliography, the outcome of the reported cases of RHD in pet rabbits has a guarded prognosis, resulting in all cases in the death of the animal.
References
Lavazza, A.; Capucci, L. Chapter 3.6.2.—Rabbit haemorrhagic disease. In Manual of Diagnostic Tests and Vaccines for Terrestrial Animals 2021; OIE: Paris, France, 2021; pp. 1389–1406.
Capucci, L.; Cavadini, P.; Lavazza, A. (2022). Viral haemorrhagic disease: RHDV type 2 ten years later. World Rabbit Science. 30(1):1-11. https://doi.org/10.4995/wrs.2022.16505
Marques RM, Teixeira L, Aguas AP, Ribeiro JC, Costa-e-Silva A, Ferreira PG. Immunosuppression abrogates resistance of young rabbits to Rabbit Haemorrhagic Disease (RHD). Vet Res. 2014 Feb 4;45(1):14. doi: 10.1186/1297-9716-45-14. PMID: 24490832; PMCID: PMC3926702.
Abrantes, J.; Lopes, A.M. A Review on the Methods Used for the Detection and Diagnosis of Rabbit Hemorrhagic Disease Virus (RHDV). Microorganisms 2021, 9, 972. https://doi.org/10.3390/microorganisms9050972
Carvalho CL, Duarte EL, Monteiro M, Botelho A, Albuquerque T, Fevereiro M, Henriques AM, Barros SS, Duarte MD. Challenges in the rabbit haemorrhagic disease 2 (RHDV2) molecular diagnosis of vaccinated rabbits. Vet Microbiol. 2017 Jan;198:43-50. doi: 10.1016/j.vetmic.2016.12.006. Epub 2016 Dec 5. PMID: 28062006.