Unit 2 Flashcards

Question

What are economic and welfare costs of livestock schistosomiasis?

Answer 1

Production model: - Herd composition - Production parameters, i.e. reproduction, yields, productive life, replacements, mortality Partial budget analysis: - Reduced costs - Reduced income - Additional income - Additional costs New treatments: Costs, reduction of impact - Cost-benefit analysis - Cost-effectiveness analysis

Answer 2

Substantial socio-economic and welfare costs of livestock schistosomiases Animal reservoirs: For and against evolution of praziquantel resistance

Answer 3

Water, Sanitation and hygiene. Prevention always better than cure, this prevents schistosomiasis infection!

Answer 4

Testing = urine tests, dipstick, looking for worms etc Treat = if at least one positive is detected, the WHOLE herd is treated Implementing TnT at herd level 2022-2030 could suppress infection and, in lower prevalence settings reach 2030 'elimination' targets

Answer 5

Praziquantel Tenicure Tenicure plus

Answer 6

1. Eggs: The life cycle begins when eggs are excreted in the feces or urine of infected humans into freshwater bodies, such as lakes, rivers, or ponds. 2.Miracidia: Once in freshwater, the eggs hatch, releasing free-swimming larvae called miracidia. 3. Penetration of Intermediate Host: Miracidia penetrate specific freshwater snails, where they undergo asexual reproduction and develop into sporocysts, which in turn produce cercariae. 4. Release of Cercariae: Cercariae, the infective stage for humans, are released from the snails into the water, where they can penetrate the skin of humans who come into contact with contaminated water. 5. Migration and Development: Once inside the human host, cercariae shed their tails and migrate through the bloodstream to the liver, where they mature into adult worms. 6. Mating and Egg Production: Adult male and female worms pair up and migrate to the veins of the intestine (Schistosoma mansoni and Schistosoma japonicum) or bladder (Schistosoma haematobium), where they mate and produce eggs. 7. Excretion of Eggs: Some eggs are passed through feces or urine back into freshwater, continuing the cycle, while others become lodged in tissues, leading to the symptoms and complications of schistosomiasis.

Answer 7

New species New place New tropism/viral characteristics

Answer 8

African swine fever West Nile virus in USA - Humans, horses and birds Feline coronaviruses - Change in tropism Avian influenza - H5Nx

Answer 9

Animal and human health Economic cost Conservation Viruses evolve and change

Answer 10

Domestic Animal disease Human disease Environment Wild animal disease

Answer 11

1. Agent only in animals no transmission to humans 2. Primary infection transmission to humans from animals 3. Limited outbreak transmission to humans from animals or (few cycles) from humans 4. Long outbreak transmission to humans from animals or (many cycles) from humans 5. Exclusive human agent transmission to humans only from humans

Answer 12

Virus circulates in animals How many viruses are there? Estimated ~1.7 million undiscovered viruses in mammals and birds 200+ known viruses can infect humans Recent paper discovered 100,000 unknown RNA viruses

Answer 13

Viral emergence from animals to humans How often does this happen? Anything that brings you into closer contact - zookeepers are a problem. Farming. Live poultry markets. Pets. Hunting wild animals

Answer 14

Was SARS-CoV-2 a one-time event? - Except for MERS and SARS Sequencing unknown serious viral infections - Coronaviruses from dogs, pigs, camels One study estimated: - 60,000 coronavirus spill overs in SE Asia per year VIRUSES EMERGE ALL THE TIME!!!!! Viruses can emerge wherever animals and humans interact: Farming: - E.g. likely measles from rinderpest - Live markets Pets Hunting - Linked to Ebola outbreak - Scavenging animals Zoos - Simian foamy virus prevalence in zookeepers Emergence more common from domestic environments than wildlife Viruses jump from humans to animals as well!! Most virus infection from animals come from domestic animals and domestic environments, wildlife zoonosis is extremely rare!!!

Answer 15

Humans can transmit viruses to animals SARS-CoV-2 - From humans to mink... And back into humans ---> Spread limited so far - Humans to deer SWINE FLU - Mixing vessel for human and avian influenza - 2009 H1N1 pandemic --> Triple reassortment inputs of human, avian and swine --> Spillback into humans

Answer 16

Touch Oral/faecal Respiratory Blood borne Vector borne Sexually transmitted

Answer 17

Human behaviour determines transmission: - Need behaviour experts Vector behaviour: - Can be modelled - Affected by climate change - Dengue - 2.25 billion more people at risk

Answer 18

PANDEMIC - global spread - Global travel - Exponential growth

Answer 19

SARS-CoV-2 - Variants increased transmission Zika - A single mutation increased probability of microcephaly Virus does not have to evolve to become less pathogenic! - Avian influenza becomes highly pathogenic in poultry

Answer 20

Lots of animal to human interactions: - H7N9 - Rarer viruses - many we may not even know about If spread limited - will fizzle out Why don't they lead to pandemics? - R0 <1 - Restriction factors - Ecological factors --> Run out of susceptible hosts - Human factors --> Infection control to prevent spread

Answer 21

1. Spillover 2. Limited transmission (outbreak) 3. Sustained onward transmission (epidemic) A combination of evolution and ecology dictates how pathogens move between stages Extended infection. Immunocompromised people might be more problematic!

Answer 22

Discussion - what would make a virus more likely to emerge in pigs? Virus and environmental/ host factors - Shared with similar species - Virus can infect lots of species - Shared immunity - Proximity of donor and recipient populations - effectiveness of immune response in clearing virus - size/density of donor and recipient - Ability of virus to recognise and replicate in host cells - variation and adaptability of viruses

Answer 23

Increased human population - More contact with animals Increased animal population - Mass farming Habitat destruction - Contact with more/ different species Global interconnectivity - Increased probability of exponential spread Climate change

Answer 24

Endemic in sub-Saharan Africa Ticks and pigs/warthogs - Ticks live in warthog burrows High mortality in pigs

Answer 25

Portugal in 1957 - Eradicated in 1999 Long-term persistence - Virus survives in frozen meat In Europe 2007 - Pig/pig contact - Spread through wild boars China 2018-19 - Reported 1,000,000 pig deaths - Actually >40% hog population???? - 1 in 4 pigs died in a year worldwide - Livestock movement/backyard farms Human activity - Virus in domestic animals - Virus in wild animals DON'T FEED PORK TO PIGS

Answer 26

Bats --> Horses in Australia - Faeces, urine, chewed up pulp - Can spread horse to horse - Occasionally horse-human Rare but often fatal (75%) - 84 horse deaths recorded

Answer 27

El Niño Leads to food shortage - Winter food stress Leads to spillover - Bats shed more virus - Move nearer humans

Answer 28

Bats feed on eucalyptus nectar In 2020: - Mass flowering event --> Red gum forest --> 240,000 bats Habitat destruction of native winter flowers ONE HEALTH SOLUTION - RESTORE NATIVE HABITAT!!!

Answer 29

Eradication of rinderpest = Increase in grazing wildebeest Less fire = more trees!!

Answer 30

Understanding anthropological factors - Especially money Small project in Madagascar - Provide healthcare - Preserve forest

Answer 31

Can you prevent spillovers? - Surveillance One health protects wild animals, domestic animals, humans and the environment Can a One Health approach always help? Is basic healthcare better than surveillance?

Answer 32

Mechanical transmission: Virus contaminated blood remains on mouthparts, fleas and mosquitoes transmit myxomatosis in rabbits, horse flies transmit equine infectious anaemia (a retrovirus) True arboviruses (Arthropod-borne viruses): Virus replicates in the arthropod vector as well as the vertebrate host

Answer 33

True arboviruses replicate in both the vertebrate and invertebrate host. The main arthropod vectors of viral diseases are mosquitoes (particularly Aedes and Culex), ticks, sandflies and midges Often the principal vector species appears to be driven by opportunity (especially for mosquitoes and midges)

Answer 34

Human host ⇌ Arthropod vector ⇌ Other vertebrate host

Answer 35

These are pathogens that normally cycle between vertebrate and invertebrate hosts and replicate in both Concept of reservoir host: Livestock ⇌ People ⇌ Wildlife ⇌ Livestock

Answer 36

Bird ⇌ Mosquito ⇌ Other animals/humans Key concepts: Dead end hosts = susceptible hosts that do not develop sufficient levels of virus in the blood to transmit the virus back to the arthropod for onward transmission Incidental hosts = Susceptible hosts that are not important for the epidemiology of disease in the maintenance host.

Answer 37

FLAVIVIRIDAE > FLAVIVIRUS - Dengue - Yellow fever - Zika virus - Tick-borne encephalitis - Japanese encephalitis - Kyasanur forest disease - St Louis encephalitis - Powassan virus - Alongshan virus - Usutu virus - West Nile virus ASFAVIRIDAE > ASFIVIRUS - African Swine Fever TOGAVIRIDAE > ALPHAVIRUS - Ross River Virus - Venezuelan Equine encephalitis - Eastern Equine encephalitis - Chikungunya BUNYAVIRIDAE - Crimean-Congo Haemorrhagic fever - Rift Valley Fever - Heartland virus RETROVIRIDAE > ORBIVIRUS - Bluetongue - African horse sickness

Answer 38

Febrile illness with rashes and arthritis (O'nyong-nyong, Chikungunya, Dengue) Meningitis, encephalitis (equine encephalitis, Japanese encephalitis, West Nile, La Cross, Colorado tick fever) Haemorrhagic fever (Yellow fever, Dengue, Rift valley fever, Crimean-Congo Haemorrhagic fever virus)

Answer 39

Effective healthcare - detection, prevention Species biodiversity - loss of habitat leading to - concentration of susceptible hosts - livestock spacing Habitat spacing - intensification of agriculture Increased vector population - water (still) - rainfall Arboviruses infect and replicate in both insects and vertebrate hosts BUT The genomes of these pathogens are relatively simple.

Answer 40

Form the nucleocapsid and envelope proteins of the virus

Answer 41

Replicate the virus genome, process polyproteins and mediate intracellular host-virus interactions.

Answer 42

FLAVIVIRUS: - prM/E - Lipid bilayer - Nucleocapsid (C) ALPHAVIRUS: - E1/E2 - Lipid bilayer - Nucleocapsid (C)

Answer 43

Mosquito borne flavivirus (aedes aegypti, aedes albopictus, ~10dpi) Once infected, a female mosquito can transmit virus for the rest of her life. Transovarial transmission to larvae via eggs is possible 3.9 billion people at risk of Dengue infection (~96 million cases and 500,000 hospitalisations annually) In humans, initial infection with Dengue generally results in relatively mild febrile illness In humans, Dengue circulates as 4 distinct serotypes During a second exposure people are at much higher risk of developing severe Dengue (Dengue haemorrhagic fever, DHF, or Dengue Shock syndrome, DSS) the more severe forms of the disease Medical care reduces the chance of death from severe Dengue from 20% to 1%

Answer 44

Transmission in most places is Human-Mosquito-Human Sylvatic Dengue is seen in primates (Malaysia, Guinea, Ivory Coast, and Burkina Faso) Evidence is that spill over of syllabic Dengue into the human population is rare. Sylvatic and human strains are distinct.

Answer 45

Sylvatic dengue refers to a form of dengue virus that is primarily maintained and transmitted in a sylvatic or forest environment, as opposed to urban or suburban settings where dengue is typically observed.

Answer 46

Sylvatic dengue replicates well in human cells + humanised mice Sylvatic dengue isolated from human DF and DHF cases (Africa, 1960s and 2009; Malaysia, 2005 and 2008). All based on sequence analysis. However, molecular clock analysis of human and dengue sequences suggests that monkey strains first emerged in the human population 126-320 years ago (DEN-1, 126; DEN-2, 195, DEN-4, 320) and have continued to adapt to the human host since then.

Answer 47

Dengue has spread worldwide since the 1950s and now affects more people than any other arbovirus In areas where there are urban and syllabic (endemic and enzootic) cycles of Dengue evidence suggests that these are separate but with potential for occasional spillover into humans Where spillover does occur there is little evidence for long-term maintenance of syllabic strains in the human population.

Answer 48

47 countries in Africa, and Central and South America are endemic (or have regions that are endemic for yellow fever) Mosquito borne flavivirus (Aedes aegypti - urban and arboreal Aedes species, e.g. Aedes africanus, Aedes luteocephalus Once infected, a female mosquito can transmit virus for the rest of her life Transovarial transmission to larvae via eggs is possible

Answer 49

Despite an EFFECTIVE VACCINE having been available since 1958, ~1.7 million yellow fever infections occur in West Africa annually with 29,000-60,000 deaths Disease is mild febrile illness in majority of infected people but progresses to more severe disease (jaundice, renal disease, haemorrhage) in 20-25% of cases. Disease epidemiology is much more as an 'outbreak' type disease: Periods of low disease incidence followed by epidemic or epizootic Unlike Dengue, Yellow fever is not usually sustained in the human population following the outbreak Only a single serotype (Dengue has 4), there are genetic clades but these are divided by geographic area rather than species West African primates seem resistant to clinical signs although they have sufficient viraemic to transmit back to mosquitoes South American primates generally have more severe disease with YFV infections

Answer 50

Generally methods aimed at preventing the spread of emerging arboviruses have been ineffective Local control in endemic/enzootic scenarios has some evidence of success Eg. Vaccination Removal/covering water Personal and household controls (screens, clothing) Vector surveillance Insecticides/repellants Sterile/self limiting male mosquitoes Wolbachia

Answer 51

PROS: Long-term, proven effective CONS: Cost, DIVA, Wildlife

Answer 52

PROS: Community involvement, reduce numbers of adult mosquitoes CONS: Difficult to ensure all breeding sites are covered

Answer 53

PROS: Community involvement CONS: Cost, rely on people using them

Answer 54

PROS: Allows risk to be assessed in an area CONS: Cost

Answer 55

PROS: Immediate CONS: Cost, environment impact, scale, insect resistance

Answer 56

PROS: Reduces mosquito population CONS: Temporary? Genetic modification

Answer 57

PROS: Reduces ability of mosquito to transmit (Dengue), spreads through population CONS: Some suggestion infectivity of some pathogens may be enhanced * Wolbachia is bacteria to infect arthropods

Answer 58

ON AN ANNUAL BASIS - 10 million active cases - 1.5 million deaths - Retained title of leading cause of death infectious disease --> COVID disruption WHO END TB STRATEGY - 90% reduction in death by 2030 - Sustainable development goals CURRENT TREATMENTS - Drugs, long regimens - multi-drug resistant TB (MDR TB) and extensively drug resistant TB (XDR TB) - Bacille Calmette-Guérin (BCG) Vaccine not effective against adult TB

Answer 59

Bovine TB in cattle Zoonotic TB (zTB)

Answer 60

Bovine TB in cattle: - High prevalence in Africa, Asia and South America - UK, Ireland, Spain and New Zealand - Wildlife reservoir Control: - Surveillance system in live herds and meat inspection - Slaughter - Economic burden

Answer 61

zTB is extra-pulmonary Contaminated milk and meat Diagnostic and treatment challenges WHO - zTB reduction part of the End TB by 2030 strategy

Answer 62

bTB is a NOTIFIABLE disease. - The World Organisation for Animal Health (WOAH) lists bTB as a notifiable disease because of its: - Socio-economic importance - Public health importance Owners have to report at a national level if they suspect an incidence of bTB in their livestock. IT IS A LEGAL OBLIGATION Chain of events to control

Answer 63

1. Surveillance 2. Breakdown management 3. Reduce risk of TB from badgers 4. Other disease prevention

Answer 64

TB caused by a group of gram-positive bacteria known as the Mycobacterium tuberculosis complex (MTBC) Human adapted species: - M.tuberculosis - M.africanum Animal adapted species: - M.bovis (broad inc cattle and wildlife) - M.caprae (goats and sheep) - M.microti (voles) - M.pinnipedii (seals and sea lions) - M.orygis (number of hosts) - M.mungi (mongoose) ALL GENETICALLY VERY SIMILAR >99% IDENTITY

Answer 65

The infection specificity of certain pathogens to particular hosts. This type of tropism explains why most pathogens are only capable of infecting a limited range of host organisms

Answer 66

Mycobacterium bovis infects cattle and it seems able to maintain within the cattle population because of cattle to cattle transmission It can spill over into human hosts in a zoonotic event and cause disease There is limited evidence of human to human transmission Evidence that M.bovis is slightly less virulent to humans than the human-adapted mycobacterium tuberculosis.

Answer 67

Low resolution methods for genotyping have shown that there are four clonal complexes of M.bovis AF1, AF2, EU1, EU2

Answer 68

SPILLOVER HOSTS: - Disease does not exist unless there is reinfection from the maintenance hosts - E.g ferrets are considered to be spillover hosts as there is very little intraspecies transmission between ferrets MAINTENANCE HOSTS: - Disease persists without an external source of reinfection - African buffalo in South Africa where an initial spillover event from livestock was thought to happen, however buffalo are able to transmit TB among themselves but also other wildlife and they are considered to be maintenance hosts for bovine tuberculosis

Answer 69

Direct transmission - close contact

Answer 70

Direct or Indirect Respiratory (direct and in close proximity) Ingestion (indirect through environment)

Answer 71

1901-1911 - Royal Commission conducts research Zoonotic risk from M.bovis infection in cattle and milk Extra-pulmonary TB and cervical lymphadenitis (Scrofula) 10-30% human TB due to M.bovis The introduction of the test and slaughter programme was very effective in reducing bTB in the herd and until about 40 years ago prevalence levels were around 0.01%

Answer 72

Peaking at 72hrs post injection Two different mycobacteria antigen mixtures improves specificity Whole blood interferon-y (IFN-y) release assay is an ancillary test for retesting skin test reactor cattle (Bovigam) - An improved sensitivity over skin testing

Answer 73

1908 - compulsory pasteurisation laws Test and slaughter policy - testing and removal of positive reactors from the herd Abattoir surveillance Epidemiological investigation of outbreaks UK - £500 million - £1 billion to control the disease in England in the last 10 years

Answer 74

A uniform cattle farming system Stringent test interpretation Financial compensation for cattle slaughtered The absence of an M.bovis wildlife reservoir

Answer 75

YES The absence of surveillance for bTB in humans in countries where bTB is endemic The challenges in differentiating between mycobacterium bovis and mycobacterium tuberculosis in countries with a high TB burden The lack of standardisation of prevalence studies (limited by inadequate sample sizes and study designs)

Answer 76

They influence treatment options Mycobacterium bovis is ALMOST universally resistant to Pyrazinamide!

Answer 77

OCCUPATIONAL RISK FACTORS: - Animal husbandry workers - Abattoir workers - Dairy workers - Live market workers - Veterinary medicine personnel HOST FACTORS: - HIV-positive persons CULTURAL: - Consumption of unpasteurised milk As LMICs make strides to control tuberculosis in humans, it is very likely that zTB will develop into a more significant public health threat because the prevention and control strategies used to address M.tuberculosis, which focus predominantly on human to human transmission, will have very little effect on the prevention and control of zTB, since the latter is primarily transmitted via food ingestion and animal handling.

Answer 78

IMPROVE THE SCIENTIFIC EVIDENCE BASE: - Collect and report more complete and accurate data - Improve diagnosis in people - Address research gaps REDUCE TRANSMISSION AT THE ANIMAL-HUMAN INTERFACE: - Ensure safer food - Improve animal health - Reduce the risk to people STRENGTHEN INTERSECTORAL AND COLLABORATIVE APPROACHES: - Increase awareness, engagement and collaboration - Develop policies and guidelines - Implement joint interventions - Advocate for investment