Healthy Pop Block 2 Epidemic Diseases

Encephalitis outbreak in NYC

1. dead crows found

2. many elderly people diagnosed and samples sent to CDC

3. mosquito control implemented

4. Tracey McNamara suspected bird and human illness related

5. confirmed flavivirus

West Nile Virus outbreak NYC 1999

1. mosquito control program

2. came from people smuggling birds into US

3. By 2003 in most of US

4. thousands of infected humans and birds

Rift Valley Fever Outbreak

1. production losses due to abortions in animals

2. mosquito spreads disease

3. outbreak in Kenya in early 1900s

4. spread to Egypt in 1977-1978

Important RVF Outbreaks

1. 1987 - Sengal, Africa

   1. not associated with rainfall, opening of Diama dam

2. 1997-1998 - Kenya, Africa

   1. largest human outbreak reported

3. 2000-2001 - Saudi Arabia and Yemen

   1. first outbreak outside Africa

4. 2003 - Egypt

   1. all cases Egyptian farmers

5. 2011 - South Africa and Namibia

   1. previous sporadic cases

6. 2013-2014 - Mauritania and Senegal

   1. sporadic animal cases

7. 2015 - Mauritania

   1. 31 cases and 8 deaths

RVF Outbreaks

1. virus endemic in tropical Africa

   1. cyclic epidemics every 5-20 years related to development of susceptible animal populations

2. associated with heavy rainfall

   1. peak in late summer

3. related to human activities like dams

Aswan Dam importance

reduced RVF by controlling floodwater mosquito breeding sites

hosts of RVF

1. mosquitoes = reservoir host

2. ruminants = amplifying hosts, reservoir for humans

3. biting flies can be secondary vectors

prevention of RVF

1. vaccination of ruminants

2. avoid and control vectors

3. personal protective equipment

4. avoid contact with infected tissues

5. restrict movement of animals

6. precautions when traveling

control of RVF

1. do not slaughter sick animals

2. wear PPE

3. avoid contact with infected tissues

4. greatest risk to travelers

5. clean and disinfect animal housing

Nipah Virus

1. emerged in 1998 in Southeast Asia

2. initially misdiagnosed

3. most cases have contact with pigs

4. fruit trees near pigs at index farm

5. fruit bats reservoir

6. pigs were amplifying host

Transmissible Spongiform Encephalopathies

1. Human

   1. Creutzfeld-Jakob Disease

      1. sporadic

      2. Iatrogenic

      3. Familial

   2. Kuru

      1. from cannibalism

   3. Gerstmann-Straussler Syndrome

2. Animal

   1. Sheep and Goats

      1. scrapie

   2. Chronic Wasting Disease

      1. elk, deer, moose

   3. Transmissible Mink Encephalitis

      1. mink farm

Nature of TSE agents

1. unconventional virus

2. incomplete virus

3. prion or abnormal protein

4. resistant to heat, UV, radiation, and disinfectants

5. survives in tissues after death

6. no inflammatory response in host

BSE/Mad Cow Disease

1. first case in UK in 1986

   1. found in cow

2. First epidemiologic study

What were findings of first epidemiologic study of BSE?

1. extended common source epidemic

2. association identified b/w feeding ruminant source protein supplements

3. incidence higher in dairy than in beef

4. larger herds at greater risk of having cases

5. no evidence of exposure to pharmaceuticals

Origin of BSE

1. disease jumped species from scrapie in sheep

2. early 1980s rendering of carcasses changed

3. ban of ruminant-source protein feeds in UK in 1988

4. 1989 human consumption of specific bovine offals banned

Incidence of BSE

1. epidemic peaked in 1992/1993

2. epidemic continued after feed ban

3. spread north and east

4. in 1996 ruminant protein banned in pig and poultry feeds

5. 63% dairy and 27% beef

6. 185,000 total cases

7. 61% of all dairies had at least 1 case

Other countries with BSE

1. native cattle in Belgium, Ireland, Northern Ireland, France, Netherlands, Portugal, Switzerland, japan, Canada, USA

2. imported cattle in Denmark, Canada, Falkland Islands, Germany, Italy, Oman, and USA

3. no known cases in cattle imported from UK to US

4. over 95% of all BSE cases were in UK

transmission of BSE

1. food-borne disease

2. infectious bovine tissues

   1. brain, spinal cord, and retina

3. affected cattle fed to zoo cats

4. feeding of contaminated feed to wild ungulates

BSE and CJD

1. 10 cases of new variant of CJD b/w 1994 and 1995

2. patients younger than normal

3. CJD variant distinguishable from old CJD

Human health concerns for BSE and CJD

1. linked to people eating contaminated beef in 1980s

2. 170 total cases

3. human epidemic near its end

4. genetic susceptibility for all cases

5. possibility of blood borne transmission

BSE restrictions

1. banned importation of live ruminants

2. restricted importation of many ruminant products

3. targeted surveillance for “high-risk“ animals

   1. adult animals with neurological signs

   2. non-ambulatory downer cows

   3. rabies-negative cattle

   4. cattle dying on farms

USDA precautions

1. 1997 = import restrictions expanded to include all European countries

2. 1997 = FDA animal feed rule

   1. banned most mammalian proteins as food source for ruminants

3. 2002 = 20,000 animals tested for BSE

4. 2012 = 40,000 animals tested for BSE

When did BSE hit North America?

in 2003 it was in Canada first and then spread to USA by end of 2003, last case was in 2012

Global BSE pandemic

BSE has spread to 23 countires with 200,000 cases

USDA first response to BSE

1. all downer cattle banned from human food

2. suspect cattle carcass held until BSE test results received

3. specified risk material prohibited from human food chain

   1. cattle > 30 months of age - neurological tissues

   2. all cattle = distal ileum and tonsils

4. additional process control for advanced meat recovery system

   1. prohibition of spinal cord tissue, dorsal root ganglia, and skull

   2. routine testing by FSIS

5. prohibition of air-injection stunning of cattle at slaughter

USDA continued precautions for BSE

1. enhanced surveillance for BSE

2. high risk cattle

   1. non-ambulatory, CNS problems, BSE signs: wasting, injury, dead

3. 667,767 tested with only 2 positive

Introduction of Bovine TB to America

1. cattle introduced from Spain in 1500s

2. cattle introduced from North Europe in 1600s

History of US Bovine TB eradication

1. 1891 evaluation of Koch’s old tuberculin as diagnostic tool

2. 1897 first state government-initiated testing

3. 1906 first federal testing in preparation for eradication program

4. 1908 TB testing required to enter fairs

5. 1911 municipal regulations requiring milk pasteurization or dairy herd certification*

6. 1917 US congress funds state-federal cooperative bovine TB eradication program

Importance of state-federal cooperative eradication program for bovine tuberculosis

1. utilized Koch’s old tuberculin for intradermal skin test

2. whole-herd testing and slaughter of all reactors

3. testing applied by geographic region

4. got reactions from 5% to 0.1% over 35 years

5. 1965 whole-herd testing ended

6. slaughter surveillance becomes primary method of identifying infected herds

7. traceback with intradermal testing of herd of origin or exposed cattle

8. 1973 began applying comparative cervical test to confirm reactors

Slaughter Surveillance Program for Bovine TB

1. suspect carcass identified at slaughter, samples submitted to federal lab

2. positive histopathological or microbiological result initiates federal follow-up investigation

Epidemiologic follow-up investigation of Bovine TB

1. testing of herd of origin

2. secondary surveillance

   1. adjacent herd testing

   2. tracing cattle movements into and out of herds

   3. high-risk area testing

TB in Michigan

1. 1994 - hunter found deer with M. bovis lesions

2. testing of deer and cattle revealed infection in NE Michigan

3. infection also found in elk, coyotes, raccoons, black bears, bobcats, and opossums

Strategies for eradication of TB in wildlife

1. reduce deer population densities

2. reduce man-made aggregations by restriction of baiting and feeding

US Brucellosis eradication timeline

1. 1934 - state-federal cooperative brucellosis eradication program begins as test-and-slaughter program

2. 1936 - trial of strain 19 vaccine

3. 1940 - vaccination added to eradication program

4. 1945 - funding for full eradication program

5. 1952 - dairy cattle surveillance with milk ring test

6. 1955 - set 1975 as target for eradication

7. 1955 - all milk required to be from brucellosis-free herds

8. 1960 - market cattle surveillance implemented

Primary components of brucellosis eradication in US

1. dairy cattle surveillance (screen pooled milk)

2. beef cattle surveillance (screen market cattle)

3. calfhood vaccination

Dairy cattle surveillance for brucellosis

1. all herds tested 2-3 times per year

2. pooled milk tested using milk ring test

3. positive test results in individual testing

4. epidemiologic follow-up of positive herds

Beef cattle surveillance for brucellosis

1. all cattle 2+ years of age tested at slaughter

2. all beef cattle 2+ years of age tested at market

3. all dairy cattle 20+ months of age tested at market

(steers and spayed heifers are exception)

human brucellosis infections in US

more than half of cases were slaughter plant workers

Brucellosis in wildlife (Yellowstone)

1. elk

2. moose

3. bison

4. predators are mechanical vectors

   1. coyotes, crows, vultures, bears

Brucellosis in bison

1. goal to be brucellosis free by 2010

2. leave park in winter to feed

3. 50% seropositive

4. congregate at calving

Brucellosis in elk

1. exposed to brucellosis at winter feeding grounds

2. isolated at calving

3. less disease transmission b/w herdmates

similarities b/w bovine TB and brucellosis

1. both diseases have transitioned from primarily livestock to wildlife reservoirs in US

2. foodborne zoonotic transmision no longer important

3. direct transmission from wildlife reservoir into livestock populations now primary concern