Emerging and re-emerging zoonotic diseases

Question 1

Significant zoonotic diseases

Answer 1

○ Severe acute respiratory syndrome (2003-4)
○ West Nile Fever (1998-2004)
○ Hendra virus (1994)
○ Menangle virus (1997)
○ Monkey pox (2003)
○ Nipah virus (1998-9)
○ Hantavirus (1993)
○ Swine hepatitis E virus
○ Pandemic Swine Flu H1N1 (2009)
○ Hantavirus in pet rat breeder in the UK
○ (COVID19…)

Question 2

New bacterial zoonoses since 1976

Answer 2

Capnocytophage canimorsus: dogs, global

Campylobacter

E. coli O157:H7: ruminants, global

Borrelia burgdorferi: tick borne, global

Helicobacter pylori and spp: dogs, cats, global

Ehrlichia chafeensis: herbivores, dogs, US

Bartonella henselae: cats, EU, USA

Rickettsia felis: flea borne, USA

Question 3

Emerging viral zoonoses since 1990 (12)

Answer 3

Sin Nombre virus (Hantavirus)

Sabia virus (Brazilian haemorrhagc fever virus)

Hendra virus (equine morbilivirus)

Bat lyssavirus

Menagle virus

Nipah virus (porcine paramyxovirus)

Influenza H9N2 and H5N1

West Nile Fever virus (US)

SARS virus

Monkeypox virus

Swine Hepatitis E

Pandemic Swine Flu H1N1

Question 4

Zoonoses that have jumped from wildlife reservoirs to humans through bushmeat hunting and consumption in Africa

Answer 4

○ HIV
○ HTLV
○ Ebola Virus (Marburg Virus)
○ Monkeypox Virus
○ Simian Foamy Virus
○ ?SARS-CoV-2?

Question 5

Likely origin of Diphtheria

Answer 5

Corynebacterium diphtheriae

Domestic herbivores

Question 6

Likely origins of Influenza

Answer 6

Orthomyxovirus

Ducks, pigs

Question 7

Likely origins of measles

Answer 7

Morbillivirus

Cattle

Question 8

Likely origins of mumps

Answer 8

Paramyxovirus

Possibly pigs

Question 9

Likely origins of rotavirus A

Answer 9

Rotavirus

Domestic herbivores

Question 10

Likely origins of smallpox

Answer 10

Orthopoxvirus

Camel pox closest

Question 11

Vesicular erythema of swine

Answer 11

Acute febrile disease of pigs characterised by vesicles and erosions in the mouth and on the snout, feet, and teats

Repeated outbreaks in USA 1932-1950s

Associated with cheap animal feed from California

Led to requirement to cook swill before feeding

May have resulted from the feeding of marine mammal meat and fish during the great depression (caliciviruses)

Question 12

Severe acute respiratory syndrome (SARS)

Answer 12

First described in Nov 2002 in Guangdong Province of China

By June 2003:
○ 8349 illnesses reported
○ 812 died (case fatality 5-10%)
○ Global

Coronavirus identified in 2003
○ Coronaviruses responsible for 25% of all human colds
○ Widespread in other species: cats, birds, pigs

Zoonosis
○ Same virus present in palm civets
§ Similar in Chinese Horseshoe bat (Rhinolophus spp.)
○ Huge infection pressure for humans in Guangdong civet markets

Control
○ Controls on animal sales and markets
○ Quarantine, screening, droplet-borne
○ WHO co-ordination
○ Transmission occurs after symptomatic period (important)

Question 13

West Nile Fever Virus

Answer 13

Flavivirus occurring in Africa, M. East, Asia, S. Europe
○ Low mortality in birds (humans and horses)
○ Mosquito and tick-borne
○ Human disease subclinical to encephalitis

Source of US outbreak
○ Migratory birds
○ Viraemic human traveller
○ Infected mosquitoes
○ (Bioterrorism)

Approaches to control
○ Eradication impossible
○ Active local surveillance with early control of mosquitoes
§ Vector control
§ Water control
§ Public awareness
□ DEET repellent
□ Involve in surveillance
§ Treatment
§ Vaccination

Question 14

Hepatitis E virus

Answer 14

Human hepatitis E - approx. 10% of human infectious hepatitis
○ 20% mortality rate in pregnant women
○ 186 UK cases 1996-2003
§ Most associated with travel to low and middle income countries (LIMC)
§ 9% were not travel associated - virus homologous to swine Hepatitis E in UK:
□ >55 year old men
□ Coastal dwellers (but 20% of >65yr olds live on the coast)
○ 800-1200 cases p.a. 2012-2018

1990’s: swine HEV described in pigs
○ 80% prevalence in UK pigs
○ Possibly a rodent virus carried by pigs?

Role for pig-derived Swine Hepatitis E virus in human disease
○ Association with raw pig liver consumption in Japan
○ Genotyping data
○ Association with processed pork products in UK

Question 15

Monkeypox

Answer 15

Virus of rodents in rainforests of central Africa
○ Circulates in arboreal squirrels

Risks of emergence are associated with
○ Globalisation
○ Encroachment into pristine forests

Human cases described
○ Severe in Central Africa and often milder in West Africa

Outbreak in USA in 2003 from importation of W African rodents

Large scale human pandemic of mild disease in 2022
○ Close contact spread
○ Vaccine used in high risk groups
○ (Resulted in name change of virus)

Human monkeypox in DRC
○ Fever and generalized pustular rash
○ Virus showed adaptation to humans:
§ Mortality fell
§ Human to human transmission increased
○ Most cases in <20yr olds:
§ Cessation of smallpox vaccination in 1980

Question 16

Covid-19: human <-> animal transmission

Answer 16

Zoonotic virus, likely originally from bats

Endemic transmission in humans

Widespread global infection in pet cats and dogs
○ Evidence that onward transmission is not significant

Widespread, sporadic incursions into many species in zoological collections

Widespread infection into farmed mink
○ High rates of transmission within farmed mink
○ Clear evidence of infection back to human farm workers

White tailed deer and hamsters
○ High rates of replication and transmission to and from humans