BOVINE SPONGIFORM ENCEPHALOPATHY

         BOVINE SPONGIFORM ENCEPHALOPATHY

1. Ritipsa Bhatt internship student at CVASc Pantnagar (ritipsa14bhatt@gmail.com )

2.Rahul Kumar ,internship students at CVASc Pantnagar (rkumae646@gmail.com )

3. Dr. Punit Sihag , VO Dhanush Healthcare Pvt. Ltd.(punit.vet@gmail.com)

Definition:

BSE is a sub chronic fatal non-febrile sporadic neurodegenerative disease of adult cattle . It is often called “Mad Cow Disease,” is a fatal prion disease affecting the brain and spinal cord of cattle. The word “prion” is an abbreviation for “infectious protein.”

Etiology :

Infectious protein, or scrapie-like infectious agent( prion) of very low M.wt.(non-detectable) around 35KD ( classical or cBSE).

Extremely resistant to heat and to normal sterilization processes. Sensitive to 4% sodium hydroxide,2%chlorine and steam sterilization.

Prions are abnormal variants of proteins that occur normally in cells, such as human brain cells. Suprisingly , when prions enter the body, they are able to convert their normal counterparts into more of the abnormal forms.

The difference between the normal and abnormal proteins does not lie in their primary structure (the sequence of their amino acids), but rather in their 3-dimensional folding. The abnormal intracellular PrP proteins are folded in a way that allows them to resist normal protease degradation so that over time this leads to the build-up of aggregates of prions in the neurons in the brain.

This disease belongs to a groups of disease known as transmissible spongiform encephalopathy (TSEs). It is characterized by a spongy degeneration in CNS ( Brain and spinal cord ) with neurological disorders sign.

Epidemiology:

1. Distribution : mostly in Europe , with occasional cases been confirmed in Asia (Japan) , the Middle East(Israel) and North America.

2. Host range : cattle
3. Adult cattle at a peak age onset of 4to 5 years
4. 30 times in dairy  than beef cattle .
   1. Experimentally transmitted to pigs , sheep, goats, mice , and monkeys but birds are resist.
5. Seasonal incidence: no seasonal incidence .
6. Transmission:
   1. Source :commercial feed ( meat And bone meal) contaminated with the infectious agent.
   2. Mode : ingestion of such meals.
      1. Vertical transmissionmay also occur.
      2. Not been transmitted via semen ,milk,colostrum ,urine, faces or hides.
   3. Economic impact : losses due to:
   4. Importation and exportation restriction from infected  localities and cost of control and eradication.
   5. Zoonotic impact: zoonotic producing fatal variant Creutzfeldt Jakob disease “vCJD”(Vision problem, dysphagia, irritability, insomnia, loss of speech and muscle spasm).

 Pathogenesis

Not well understood or documented. It is suggested to be similar to scrapie in sheep in which after infection, replication of the agent start in the tonsils and retropharyngeal Lymph node then subsequently disseminated to others lymph node and spleen, then by an unknown mechanism it reaches to the CNS.

Replication occur with accumulation of disease associated abnormal protein (SAFs) in the nervous tissue and finally damage the cell (vacuoles in grey matter).

Clinical signs

I.P is long (2- 8 y.) with low morbidity and 100% mortality; the course of the diseases varying from 1 to 6 months.

Loss of muscle control resulting in abnormal gait, tremors, hind limb ataxia and poor balance.

Behavioral changes may include aggression, anxiety, nervousness, frenzy, ataxia, abnormal facial expression or an overall change in temperament.

Rarely but observed, persistent rubbing or licking.

Non-specific symptoms have also been observed which include weight loss, decreased milk production, lameness, ear infections and teeth grinding due to pain.

Some animals may show a combination of these symptoms, while others not.

Once clinical symptoms arise, they typically get worse over the upcoming weeks and months, eventually leading to recumbency, coma and death.

Post Mortem lesions:-

The pathognomonic lesion is bilateral symmetric non-inflammatory intra-cytoplasmic vacuolation of neuron and gray matter.

Amyloid plaques that are associated with L-BSE prions not with the classical BSE prion or H-BSE (based on mass of unglycosilated protein fragments)

Scrapie-associated fibrils (SAF) in the affected neurons (electron microscope).

Diagnosis

1- Field diagnosis; depends on case history, clinical signs and P/M lesions.

2. Lab. Diagnosis;

Sample: Mainly CNS including, brainstem, medulla oblongata and spinal cord.

Some lymphoreticular tissues as spleen, thymus, tonsils and retropharyngeal Lymph node .

Laboratory procedures:

(There is no live animal test for BSE)

Histopathology of brain to detected microcavities. Detection of (SAF) by electron microscopy. Immunohistochemistry to detect the prion protein in the brain tissue.

Differential Diagnosis

The disease should be differentiated from all causes of nervous manifestation as following:

1.SBE or Buss disease or sporadic bovine encephalitis

Polioencephalomalacia (PE)

3. Hepatic encephalopathy;
4. Metabolic diseases such as acetonaemia, hypocalcaemia and grass hypomagnesaemia.
5. Traumatic injury to the head or back is fairly common and the signs that result reflect the site and degree of damage done to the brain and spinal cord
6. Other diseases: rabies, listeriosis, brain abscess and lead poisoning.

Treatment:

No treatment.

Control & vaccination

Control of BSE quite difficult due to absence of infection, can’t be detected in live animal .

In endemic areas: notification and quarantine on infected farms or countries with obligatory slaughter and destruction of carcasses of the infected cattle by burning or burial. There is no need for isolation of infected animals because there is no significant horizontal transmission .

Disinfection of the farms by sodium hydroxide solution, or a sodium hypochlorite solution containing 2%available chlorine.

Reduce exposures of cattleto infectious aren’t by prevention the use of bone or meat meals to ruminats from BSE or scrape infectedcattle or sheep and goats.

Prohibition consumption of bovine offal.

NO VACCINE AVAILABLE .

REFERENCES:

1. https://www.cdc.gov/mad-cow/php/animal-health/index.html
2. https://www.msdvetmanual.com/nervous-system/bovine-spongiform-encephalopathy/bovine-spongiform-encephalopathy

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