6 - One Health Flashcards
What is One Health?
It is an integrated, unifying approach that aims to sustainably balance and optimise the health of people, animals and ecosystem
What kind of approaches and concepts do we have for One Health?
Concepts should be system dynamic (connectiveness between aspects) and the approaches should be ecological, despite anthropogenic drivers.
What is the scope of One Health?
One Health covers emerging zoonoses, food security/systems, international health/development, antimicrobial resistance, human-animal bond and more.
What are SDGs and how does One Health aid them?
SDGs are sustainable development goals which aim to improve food security, poverty alleviation, climate change, social justice, peace, environmental protection and health. One Health provides framework for achieving benefits which span many SDGs.
Describe the issue of underconsumption.
Childhood stunting rates are at high levels due to low consumption of animal-sourced foods - usually aids growth, cognitive performance, motor development and increased activity in children.
Describe reliance and issue with livestock.
Livestock is heavily relied on for food security and livelihoods, also aids crop production (manure, traction), and provides financial stability.
The issue with livestock is disease, which impacts income, and can cause malnutrition, zoonotic diseases, decreased education (SDG - break cycle) etc. Another issue is that livestock die during drought season and so people seek other forms of income/food like crops.
e.g. foot and mouth disease.
Describe the issue and main driver of zoonotic diseases and give an example of where we saw this.
Zoonotic diseases are hard to manage and diagnose due to prevalent symptoms. Land-use change like deforestation and irrigation is the major driver of zoonosis spillover - causing an increased zoonotic risk. It effects reservoir host distributions, pathogen prevalence and spread.
Example: Nipah virus was due to spillover from fruit bats to pigs - proximity of pig farm to mango plantation meant the bodily fluids secreted from bats when feeding contaminated the environment, and the virus then emerged in pigs.
What is spillover?
The transmission of a pathogen between animal species.
Describe the issue of endemic diseases.
Endemic diseases are most often found in poor and disadvantaged areas due to lack of resources and access to treatment/prevention. There is a cycle of neglect that occurs where there is a a lack of disease burden data, we face diagnostic challenges and then this affects these communities.
Describe the issues of febrile illnesses.
Febrile illnesses present with flu-like symptoms and are very common in children from low to middle income countries. These symptoms are an issue as so many diseases present with them, so tend to be misdiagnosed - often as Malaria.
What are the two ways we could tackle many One Health issues?
- Target animals for protection of people
- Lower/get rid of immunisation prices.
Describe what vaccinating animals would do.
This available intervention would treat the disease at the source (reservoir) and provides a broader safety net. It would reduce disease burden on both parties and is necessary for elimination of infections with these animal reservoirs - not confined to humans.
Describe one example of animal vaccination.
Rabies Management
Post-exposure prophylaxis (PEP) is given after a bite, and mass dog vaccination is done to prevent reservoir transmission. It has the highest disease case fatality, but PEP is expensive and so there are inequalities; Those most prone do not receive vaccination.
Rabies rates are lower in areas with high vaccination rates of both dogs and humans (PEP) - most cost effective and sustainable, causing the fewest deaths.
More funds should be allocated to dog vaccination.
What is MCF and the effects of livestock vaccination?
Malignant Catarrhal Fever is a wildebeest virus which spreads to cattle in the calving season due to spread via reproductive tissue (picked up from grazing). There are no vaccines available so pastoralists must move cattle from high-grazing land to avoid this season, meaning households gain less protein, cannot consume or sell milk, and it also causes rebuilding of cattle’s body conditions.
There is a potential vaccine which would provide partial protection, and focus groups of pastoralists were made. This would improve pasture quality, food security and reduce land conflict, but could increase predation, degrade land, increase human-wildlife conflict and affect wildebeest migration.
What is the effects of immunisation prices?
Childhood immunisation for polio is free, but not for rabies, and there are charging fees for animal interventions. These are not government funded and so aids the spread of rabies due to inaccessability.
What are the opportunities of One Health?
- Recognises need for integrated and ecological approaches
- Funding available
- There is expertise for One Health
What are the challenges of One Health?
- Very generalist, multidisciplinary approach so issues surrounding trust and control.
- Community engagement
- Challenges in funding for implementation of preventative measures.
What is a vaccine?
A vaccine gives a boost to the immune system to induce an antibody response which protects against an infection. It is a small harmless dose of the disease which initiates the response, meaning we have the necessary antibodies if we encounter the disease again.
What is the difference between prophylactic and therapeutic vaccines?
PROphylactic - given to healthy individuals to develop immunity.
Therapeutic - given to those previously infected and accelerates their immunity, training the immune system.
What is herd immunity and why is it important?
Herd immunity is when a large proportion of the population is vaccinated and so it is harder for infectious disease to spread.
It is important as it provides protection to communities, breaks chain of transmission and prevents unnecessary deaths. It is vital those who can get vaccinated do to ensure herd immunity as those immunocompromised and of age limitations cannot. The effort required is dependent on the R0 value - how many should be vaccinated.
What is the R0 number?
The R0 is the reproduction rate/number/ratio. It is an epidemiologic metric which describes the contagiousness and transmissibility of an infectious agent using estimations from mathematical models. It helps us see how many individuals must be vaccinated, whether we need any boosters and its efficacy.
R0 > 1 - outbreak continues
R0 <1 - ends.
What are the 5 contents of a vaccine?
- Water (bulk)
- Active ingredient (small harmless dose of disease)
- Adjuvant (extra boost if active isn’t sufficient to generate antibodies e.g. Aluminium)
- Preservatives/stabilisers (prevents contamination, prolongs shelf life, maintains quality)
- Residual traces (something used to make vaccine (egg))
What is the R0 value in terms of spread of infection?
It describes the average number of secondary infections caused by a single host in a completely susceptible population.
R0 = 2, every 1 infects 2, maintaining chain of infection.
R0 = 1, not exponential spread but sufficient to persist, every infection replaces itself (1=1).
R0 < 1, outbreak will end and pathogen will go extinct.
How are vaccinations carried out in the UK, give an example.
The UK uses strict routine immunisations which gives an order and age to when you should receive each vital vaccine for it to be effective.
e.g. MenACWY - four strains of meningitis (~12 years - before sexual activity)
MMR vaccine
Why may someone be given an extra vaccine (4)?
High risk groups:
- immunocompromised
- pregnant (antibodies can move to foetus too)
- born to HepB infected mother
- in high TB incidence area
What are the 8 factors we should consider in order to eradicate a virus?
- Effective and safe (cheap, stable (will not adapt to pressure) and little doses)
- Lifelong natural immunity induced
- Short period of communicability (confined to humans easier to vaccinate)
- Highly characteristic clinical symptoms
- Easy and reliable means of diagnosis
- No nonhuman/environmental reservoirs
- Genetically stable causative agent
- Seasonality of occurrence (more targeted)
What are three current vaccine candidates?
Polio, measles, and rubella.
What are the pros and cons of a replicating viral vaccine strategy?
- live, attenuated (replicated in other systems so no longer infectious to humans)
Pros: stimulate antibodies, T cells and mucosal immunity, single vaccine may be efficient, durable immunity.
Cons: could restore virulence, persistence in immunosuppressed, cell culture low yielding or not possible and limited shelf life.
What are the pros and cons of a non-replicating viral vaccine strategy?
- subunit, nucleic acid etc (small part of vaccine)
Pros: no risk of infection and quicker to produce.
Cons: less immunogenic, may require adjuvants/boosters, may not stimulate local IgA mucosal response.
What is Mpox and its components?
MPXV is a linear ds-DNA which is a brick-shaped virion that can be enveloped in host cell-derived membrane, and they have ITRs which ease replication via forming a ring.
What is a viral vector?
An unrelated harmless virus which is modified to deliver genetic material for the viral vaccine.
What is the poxvirus replication cycle?
- Bind
- Fuse/enter (mature - no membrane so taken in by vacuoles, enveloped - membranes fuse to enter)
- Nucleocapsid release
- Transcription
- Translation
- Replication (into viral proteins in cytoplasm)
- Lysis/budding
- Release (enveloped virions burst from cell to exit)
What is the difference between clade I and II mpox?
I - endemic to Central Africa, severe, more virulent, and can actively disable immune response
II - less virulent, endemic to West Africa.
What was MPXV declared by WHO and when?
MPXV was declared a public health emergency of international concern in 2022, but has been classified this on and off - different clades causing issue.
How does mpox spread - how does it enter, who?
Mpox can spread between animals and humans, infecting a variety of mammalian species, and it does not require an animal intermediate. It can spread from mother to foetus via placenta.
The virus enters via skin breaks, eyes, mouth, nose, and other respiratory tracts.
The animal reservoir is unknown and transmission is likely direct, but could be indirect (contamination of shared space etc).
How are mpox and smallpox linked (vaccination)?
The mpox outbreak began when smallpox was eradicated (1980s), and this could be due to the smallpox vaccine giving individuals an extra boost, and the natural antibodies for the related virus stopped being generated when we stopped vaccinating.
What are the clinical symptoms for mpox?
- takes 7-21 days to show
- mild as it is self-limiting (naturally cleared)
- lasts 2-4 weeks
- transmissible if pox lesions appear (distinctive)
- aches, fever, exhaustion
- differs from smallpox by swollen lymph nodes
- centrifugal rash spreading to extremities
What are the five stages of mpox rash?
- macule (spotted)
- papule (raised)
- vesicle (blisters)
- pustule
- scabbing (scab falls off = no longer infectious)
What are the three methods we can use to diagnose mpox?
- Real-time PCR - how much virus is present in individual, highly sensitive, fast, determines clade.
- Eliza - look for present antibodies and vaccine efficacy - IgM best. Cannot determine if individual is infected or not as Ab may be present from a previous or current infection.
- Sequencing - which virus, how it is mutating, which clade. It is unsuitable for clinical use due to pricing and training needs - use MinION sequencers instead to increase number of sequences to tackle this.
What is the treatment for mpox?
Supportive care - milder symptoms so we treat these rather than infection.
Combination therapy of three drugs may be used as they may evolve and develop resistance.
Is there a vaccine for mpox?
- smallpox vaccine protects against mpox
- two approved vaccines for both clades: MVA-BN and LC16m8.
- these are third generation smallpox vaccines which are live, attenuated.
How can we as a population prepare for an outbreak of mpox?
Community engagement, isolation, self-protection, limiting number of sexual partners, pre- and post-exposure vaccines.
What is epidemiology?
This is the study of the distribution and determinants of disease frequency and the application of this to control health problems - uses One Health at a population-level.
What is morbidity?
Frequency of disease within a population.
