African horse sickness is also one of the notifiable disease listed under classification Rio Verde family classified under the Baltimore group 3 group 3 comprises of viruses with double-stranded RNA genome the word Rio refers to respiratory and teurac orphan viruses that is these virus infect humans respiratory and intestinal tracts without symptoms some of the veterinary important viral diseases under this family are blue tongue and African horse sickness under the genus or B virus rota viral in her itis under the genus rotavirus the diseases under the genus or B virus and Cole T virus are arthropod borne viral diseases.
The disease’s under the genus rotavirus and/or Thurio virus are non arthropod borne viral diseases transmitted through fecal oral route transmission in this lecture we will discuss in detail on African horse sickness the other names for this infection are pest a aquino Africana pest a equine and / dizzy act the causative agent of diseases African horse sickness virus which belongs to genus or B virus of the family Rio Verde this virus is an arbor virus.
That is transmitted by biting majora pod-like Cooley Cadiz so the infection is a non contagious arthropod borne viral disease characterized by pulmonary and cardiac lesions affecting horse host range apart from the horse this virus also infects mules donkeys and zebras horses are highly susceptible for this infection followed by mules donkeys and zebras are least susceptible for this infection similarly high mortality rate is seen in horses followed by mules and then donkeys but the mortality is rare and zebras.
This infection is prevalent in southern Africa and northern Africa occasionally there are nine antigenically distinct serotypes of African horse sickness virus existing named from serotype one to nine identified by the virus neutralization test. India is free of African horse sickness infection last case was reported in 1963 which was serotype nine African horse sickness virus virus morphology this virus posses triple spherical capsid layered one over the other outer capsid core capsid and inner capsid.
Which encases segmented genome this segmentation may leads to genetic reassortment the entire virus is about 75 to 80 nanometer diameter vp2 and vp5 codes for the outer capsid vp2 is a serotype specific antigen and they play a major role in the antigenicity. That is virus neutralizing antigens vp3 and vp7 codes for the core capsid vp7 is a Syrah group specific antigen and v p1 v p4 and vp6 codes for the inner capsid genomic organization the genome is multipart.
That is segmented and double-stranded RNA this segmented genome may result in genetic reassortment the or b virus possess ten segments rotavirus possess eleven segments call T virus twelve segments and or three or virus ten segments so our interest. Here is on or be viral which possess ten segments each segment codes for one or two proteins the five prime end is methylated.
If a horse is infected with three similar type of viruses but different serotypes at same time due to reassortment of segments that is genetic recombination there may be evolution of new virus that may be a hybrid of this three virus this type of major change in the virus is called as energetic shift this happens due to reassortment of segments that is genetic recombination leads to evolution of new virus virus replication. This virus enters the host by endocytosis following entry the virus replicates in the cytoplasm.
Here the genome is double-stranded rnai only the negative sense RNA are transcribed and synthesis the positive sense RNA this positive sense RNA. which are similar to mRNA are translated for viral proteins these positive sense RNA are synthesized in excess so on the other side the success positive sense RNA act as template for negative sense strand synthesis later these synthesize double-stranded viral RNA and the translated viral proteins self-assembles to form virion transmission this is an arthropod borne viral infection so biting midges like coulis cadiz species can act as the principal source of this virus blood and semen from the infected animal can also source this virus this virus enters the host through infected niche by which is a biological vector.
Which may leads to increased vascular permeability edema hemorrhage and intravascular coagulation clinical manifestation four forms of this infection are seen per acute or pulmonary form also called as danke sub acute or cardiac form also called as de cope mixed form and subclinical form also called as African horse fever / acute or pulmonary form in this fever severe respiratory distress dis Nia spasmodic coughing dilated nostrils with frothy fluid oozing out redness of conjunctiva followed by rapid.
Death within few hours as noticed the picture shown here is the dilated nostrils with frothy fluid oozing out in horse in pulmonary form the picture shown here is the redness of conjunctiva in horse in pulmonary form the picture shown here is the foam from the Nerys due to pulmonary edema in horse in this form sub acute or cardiac form in it even a swelling of the supraorbital fossa eyelids facial tissues neck thorax brisket and shoulder region followed by death due to cardiac failure is noticed the picture shown.
Here is the swelling of supraorbital fossa in horse in cardiac form mixed form in this both pulmonary and cardiac signs are noticed but mild in nature that do not progress and last subclinical form or African horse fever in this mild clinical signs with fever and general malaise for short period is noticed deaths are rare in this form based on severity high mortality is observed in pulmonary form.
That is up to 95 percent followed by mixed form 70 to 80 percent and cardiac form 50 percent or more in subclinical form or African horse fever the animal will typically recovers post-mortem findings in pulmonary form severe diffused pulmonary edema Hydra thorax that is fluid in abdominal and thoracic cavity and enlarged edema Tazz lymph nodes are observed in cardiac form yellow gelatinous infiltration at head neck shoulders brisket ventral abdomen rump regions.
Hydro pericardium is observed diagnosis can be done in field level or in the laboratories field diagnosis based on the prevalence of the biological vectors like Cooley Cadiz species by signs and clinical symptoms observed like frothy fluid from Nerys redness of conjunctiva and swelling of supraorbital fossa and by post-mortem findings like Hydra thorax and hydro pericardium next laboratory diagnosis for a lab diagnosis blood paired serum samples are collected from live animal in dead animal spleen lung lymph nodes are collected.
This virus can be cultivated or isolated in lab by three ways number one embryo native egg inoculation 13 to 15 days old embryo native chicken eggs are used for this intravenous route of inoculation method is done the second method of cultivation of this viruses cell culture system BHK 21 Vera sells and insect cells can be used the third method of cultivation of this viruses animal inoculation here newborn mice are used with interest cerebral root of virus inoculation.
These are some of the laboratory tests can be done for diagnosis of this virus for antigen detection jelly’s a– virus neutralization test reverse transcriptase pcr and DNA sequencing for sarah typing is done for antibody detection complement fixation test competitive ELISA and indirectly ELISA is done in these tests known African horse sickness viral antigen is used prevention and control these are the measures followed for the prevention and control of this infection like vector control primarily done.
Here water management is done to reduce of cooley Cadiz breeding sites use of insecticides and larvicides by spraying over breeding areas and dipping of animals and insect repellents quarantine and restricted susceptible animal movement during insect activity period vaccination using live attenuated vaccine against specific African horse sickness virus serotypes of concern in a particular area is used mono valent and polyvalent live attenuated vaccine are available annual vaccination has followed in affected areas regions and countries serological surveillance identification and tracing of susceptible and potentially infected animals.