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OKAY BACK FROM THE RENDERING PLANT 🏭

Epidemiological Studies Of Mad Cow Disease Or BSE Began In May 1987

Researchers Weighed Infection Or Poisoning Or A Purely Genetic Cause

An Initial Study Ruled Out All Of Them Except Infection

The Suspected Agent Was Like The One Behind Scrapie In Sheep

Meat And Bone Meal In Cattle Feed Was The Most Likely Carrier

The Meal Was Added As A Source Of Protein

Further Studies Reinforced That Hypothesis

The Main Finding Was A Gap In BSE Rates Between Guernsey And Jersey

Both Are The Main Channel Islands Of The British Isles

The Islands Bought Commercial Cattle Feed Only From Mainland Britain

Each Island Had A Different Main Supplier

Guernsey's Supplier Used Meat And Bone Meal Relatively More Often

Jersey's Supplier Did Not Value The Meal For Nutrition Or Cost

That Was True For Most Of The Cattle Feed It Made

The Difference Between The Suppliers Arose By Chance

A Formal Case Control Study Had Begun In The First Half Of 1988

It Looked For A Link Between Meal In Calf Feed And BSE

The Analyses Were Completed In 1991

Eating The Meal In The First Year Was Linked To BSE Later In Life

That Supported The Original Meat And Bone Meal Hypothesis

The Result Also Suggested Most Cases Were Infected As Calves

Commercial Calf Feed Also Had A Greater Share Of The Meal

Simulations Suggested Cattle Exposure Began Around 1981 And 1982

That Start Seemed Sudden

Several Possible Explanations Were Examined And Ruled Out

A Marked Rise In Scrapie Among Sheep Was One Of Them

Using The Meal For The First Time Was Ruled Out Too

It Had Been In Commercial Feed For Some Decades Before

A Look At The Rendering Plants That Made The Meal Showed Changes

Plants Had Used Hydrocarbon Solvents To Extract Fat From The Meal

An Autumn 1988 Survey Found A Dramatic Drop In That Solvent Use

The Drop Matched The Suggested Start Of Cattle Exposure

Only Two Plants Still Used Solvents At The Time Of The Survey

Both Were In Scotland

BSE Incidence Was Low In Scotland And The North Of England

Most Meal Made In Scotland Had Gone Through Solvent Extraction

Solvent Use Was Likely Linked To The Low Incidence There

A Veterinary Review Links The Outbreak To Falling Solvent Use

It Says Rendering Methods Changed In The 1970s And 1980s

Those Changes May Have Let The Infectious Agent Survive Processing

BSE Was First Identified In The UK In 1986

State Veterinary Services Found It Through Routine Surveillance

Cases Appeared At The Same Time All Across Britain

The Southern Counties Of England Had A Notably Greater Incidence

Dairy Herds Saw Considerably More Of It Than Beef Suckler Herds

Incubation In Cattle Is Thought To Last From 30 Months To 8 Years

The Average Is Put At 4.5 To 5.5 Years

Once Signs Appeared Most Died Or Were Put Down Within 6 Months

Annual UK Reports Of BSE Were 446 In 1987

By 1992 They Had Reached 37,280

In 1992 Incidence Within Affected Herds Was 2.7 Percent Of Adults

The Epidemic Persisted And Grew As Infected Cow Material Was Recycled

Weekly Counts Were Highest In January 1993

Almost A Thousand Probable Cases Were Recorded Every Week Then

After The Peak Cases Fell About 40 Percent In Successive Years

By April 2005 There Were 180,780 Confirmed BSE Cases

Those Cases Came From Over 36,000 Cattle Herds

After 2010 Fewer Than 10 Cases Were Reported Each Year