Pseudorabies and rabies

• Pseudorabies disease is caused by a herpes virus which is highly contagious and it commonly affects swine.
• Pseudorabies is most often a mild disease or can be asymptomatic in pigs but it is highly fatal in cattle.
• The clinical signs of Pseudorabies include abortion, stillbirths, respiratory problems, and neurological signs which are similar to rabies thus the name, pseudorabies.
• Pseudorabies, Aujeszky’s Disease, or Mad Itch is a contagious, infectious, and communicable viral disease of livestock and pigs serve as its natural hosts.
• Pseudorabies Virus (PRV), an alphavirus from the subfamily Herpesviridae, genus Varicellovirus, has a low death rate in adult pigs and can remain hidden in the pig in a carrier state for long terms but it is deadly in cattle as recovery is rare.
• PRV is transmitted directly through nose-to-nose, sexual contact including insemination with contaminated semen or transplacental transmission and can be indirectly passed via inhalation of aerosolized virus or consumption of contaminated water, and fomites.
• This virus can live only a few hours on clean concrete or mixed in dirt, three days on plastic and steel, and two days in manure and lagoon water.
• Pseudorabies and rabies have neurological clinical manifestations, but can be differentiated through their several other clinical features.
• Clinical signs of rabies include decrease in milk production, reduced milk intake, aggression, excitation or exaggerated movements, inappetence, dysphagia, seizures, and persistent erection or penile prolapse in Bulls.
• Treatment and prevention of rabies involve antibiotics, vaccination, restriction of animals, proper fencing, and wearing of PPE during physical examination.
• Diagnosis of rabies involves post-mortem examination, Direct Fluorescent Antibody (DFA) Test, Direct rapid immunohistochemistry test (dRIT), Mouse inoculation test, Histopathology, and Enzyme-linked immunosorbent assay (ELISA).
• The most common means of infecting is through the saliva of an infected wild animal through biting.
• The pathogenesis of rabies involves a bite or scratch from an infected wild animal, entering of the virus through orifices and lacerations, initial replication at the muscles, incubation at the spinal cord, moving to the brain for extensive replication, and viral clinical manifestations at the brain.
• Transmission of rabies is via bite or bodily fluids from different infected animals such as fox, raccoon, dog, jackal and wolves.
• PRV is very sensitive to pH levels below 4 and above 9 and is dependent on the temperature.
• After natural infection, the primary viral replication site is the epithelial cells of the upper respiratory tract (nasal, pharyngeal, or tonsillar epithelium), with a viral spread and shedding, and then reaches the basement membrane (BM) and lamina propria through a single infected leukocytes to go to the circulation of blood and draining lymph nodes.
• The secondary replication happens in the CNS and uterus which leads to vasculitis and multifocal thrombosis, with an abortion of sows and in newborn piglets, and might lead to sudden death of cows.
• Clinical signs of Pseudorabies include neurological manifestations such as tremors and paddling, intense pruritus, concentrated in a patch of skin, which presents as; severe licking, rubbing or gnawing.
• Self-mutilation is common in animals affected with this disease.
• Other signs of Pseudorabies include muscular contractions, grinding of the teeth, fluctuation on the cardiac cycle, and fast, shallow breathing.
• Post mortem lesions observed in Pseudorabies are areas of edema, congestion, and hemorrhage in the spinal cord.
• Animals affected with Pseudorabies become continuously weaker, soon becoming recumbent, and then leads to death.
• Serology is not helpful in the diagnosis of Pseudorabies virus in species other than pigs as these animals usually die before mounting an antibody response.
• Pseudorabies could be diagnosed through virus isolation and tissue collection.
• Tissue samples may be collected from the section of the spinal cord that innervates the pruritic area along with the skin and subcutaneous tissues.
• There is no specific treatment for Aujeszky’s disease, except supportive care and treatment for secondary infections.
• For the prevention of Pseudorabies, make sure biosecurity program are strictly followed, isolate and test all incoming livestock, minimize and control human traffic into and within the herd, and control wildlife, rodents, and pests that may bring diseases on the farm.