Viney Co-infection

Question 1

is coinfection common?

Answer 1

it is the rule

although not always evident in lab conditions

Question 2

what is a community co-infection

Answer 2

infection with multiple species

Question 3

simple example of coinfection in all humans

Answer 3

gut microbiota
shown to have profound effects on normal health and
development.

Question 4

what are two scales of co-infection?

Answer 4

1. Macro-geographical
   - eg schistosomes and malaria distributions overlap people exposed simultaneously.
2. local scale - in households there is coinfection of schistosomes and malaria.

Question 5

describe coinfection of schistosomes and malaria

Answer 5

study of Lake Victoria
measured schistosome infection in each household. areas closer to river more infection. Serological measure of plasmodium exposure is similar. each smaller area within this has a different level of co-infection.

Question 6

what types of interactions can there be between coinfections?

Answer 6

none
negative 
positive 
dynamic
DUE TO: 
direct effects
indirect effects
comp for resources

Question 7

study of sheep coinfection

Answer 7

Haemonchus contortus - blood feeding stomach worm
Trichostrongylus colubriformis - intestinal browsing worm
- cleared sheep of worms
- Groups: 1. control, no infection. 2. T.colubriformis only (1500 per dose)
3. H. contortus only (300 per dose), trickle infections. 4. mixed infection.
- 18 weeks later, intestinal worm counts.
-Higher adult count of T. columbriformis in a coninfection.
Coinfection has no effect on H contortus.
Consequence - treatment for H contortus, will have an effect for T columbriformis too. mechanism unknown.

Question 8

what are some potential mechanisms for the positive effectsof coinfection of T columbriformis and H contortus?

Answer 8

(i) creates or improves the niche for
the other parasite
(ii) induces some immune suppression in the host, which therefore favours the other parasite (specific version)

Question 9

study of coinfection of malaria and Litomosoides sigmodontis

Answer 9

in rat - filarial nematode, adults in thoracic cavity, transmitted by ticks
Groups: 1. uninfected
2. filaria only
3. malaria only
4 co-infected
found coinfection leads to more severe disease, anaemia, compared to malaria only mice.

Question 10

how are coinfections regulated?

Answer 10

Bottom up - limited by resources, eg RBC availability for malaria
Top- down: predator based

Question 11

what was 3 conclusions of a meta analysis by graham et al 2008

Answer 11

included 54 experiments on mice, of 9 helminths and 29 microparasites
1. parasites causing anaemia provide bottom up regulation of microparasites which require RBC.
2. microparasites which dont require RBC have no effect of anaemia inducing worms.
3. coinfection impaired top down control (immune regulation) of microparasites.
more suppression of IFN gamma, = increase in microparasite density.

Question 12

what is the worst case with helminth coinfection?

Answer 12

when helminths do not impose bottom up regulation but remove top down regulation.

Question 13

what study aimed to see how a hosts microparasite susceptibility is influenced by co infections?

Answer 13

Telfer et al 2010
wild voles: Microtus agrestis
naturally infected with viruses, protozoa and bacteria.
not controlled experiments, inferred coinfections by observation.
studies cowpox, babesia (protozoan) Anaplasma and bartonella (bacteria)
found: widespread, interconnected pos and neg coinfection effects, explaining more variation in infection risk than host age or season.

Question 14

specific outcomes of vole coinfection study

Answer 14

1. babesia - 5x more predisposed to anaplasma infection, and less chance of bartonells infection.
2. anaplasma - 5xmore redisposed to cowpox.compared to voles uninfected with anaplasma.
3. if not infected then infected with cowpox, 1.89 x more likely to get babesia infection.