Parasite types
What are the major mites? who do they infect? what do they do
Chorioptic mange - cattle, horses, sheep, tail head, udder area, hind legs, common in dairy cows confined
Psoropotic mange - Cattle and sheep mite, not seen in canada, mite feces cause allergic reaction with skin, mites that suck the exudates and secretions
Sarcoptic mange - can infect cattle and sheep, dig tunnels in the skin, spend their whole life on host, dig tunnels under the skin where they deposit eggs, severe damage, hardening and thickening of skin, large folds, federally reportable
What does trichomoniasis look like in the cow
They can carry it and spread it to clean bulls
The parasite lives in the repro tract of the cow
All ages of breeding females are susceptible to infection
cows that are infected will usually conceive normally
What are examples of diseases that are infectious but not contagious
Blackleg in calves - caused by the bacterium clostridium chauvoei, which is present in soil and the intestinal tract
The bacteria can form spores that can exist for a long time, spores are dormant in muscle tissue until there are conditions with low oxygen, spores germinate and bacteria release potent toxins
calves don't pass disease directly to other calves
What is the difference between vertical transmission and horizontal transmission? Examples of diseases for vertical?
Vertical - from mother to young = Transmission from one generation to the next usually in utero or via colostrum - bovine leukemia, bovine viral diarrhea virus
Horizontal - From animal to animal - has direct and indirect contact
What does modes of transmission determine
Method of control
What do ticks do? what can that cause?
Complex life cycle - involves wildlife
bit and hang on until they have completed a blood meal
Extreme numbers can cause blood loss in wildlife
Can carry a number of diseases
How do you diagnose parasites
Look for the adult
look for the larvae
look for eggs
look for disease
Typically will need a vet to help
What is a disease that is both infectious and contagious
Salmonella
Primary spread is fecal-oral - can also be spread by fomites, feeding equipment, feed, nipple bottles, esophageal feeders
These can pass by a variety of methods from animal to animal and sometimes other species
What is direct and indirect transmission types (vectors)? Examples of disease ?
Direct - close contact (skin-skin, sexual, carcasses, excretions and secretions), contaminative (airborne, waterborne, soilborne, fomites, food borne)
= Cattle ringworm (skin to skin), tritrichomonas foetus (sexual), bovine spongiform encephalopathy (carcasses), Respiratory diseases (Secretions and excretions)
= Foot and mouth (airborne), anthrax (soilborne),
Indirect - intermediate host, arthropod vector
= BSE
How are respiratory infections spread
Many in sheep and cattle are spread by droplet transmission - Infectious bovine rhinotracheitis, bovine tuberculosis, foot and mouth
Some are spread through fomites and through indirect transmission - bovine tuberculosis and contaminated feeding areas
A small amount is spread via airborne transmission - Foot and mouth, Q-fever
What are the major protozoa
Coccidia - single celled organism, lives in the gut wall, can cause severe diarrhea in young stock, oocysts long lived in environment
Tichomonas
How do you control parasites
Understanding lifecycle can really help
Find a way to break the cycle of infection
- control feed
- Field rotation
- wildlife control
- Controlling vectors
Why is understanding infection disease transmission important
Essential to understanding disease control
What is indirect transmission
Occurs whenever horizontal transmission of the pathogen between two hosts requires another organism
Vector born pathogens cause vector borne diseases and are transmitted between vertebrate hosts by arthropod vectors
Macroparasites are carried by one or more intermediate hosts that are consumed by the final vertebrate hosts to complete a complex life cycle
What is the difference between infections in the respiratory system due to droplet transmission compared to aerosol
Droplet - close contact, droplets are defined as large aqueous bodies, fall to earth very quickly, more likely to contaminate fomites if pathogen can survive in environment
Aerosol - distant contact, aerosolized particles are infinitesimal, stay suspended in air for much longer periods of time, viruses may be more likely to be diluted and inactivated while lingering in air, this is the type of transmission that is usually referred to as airborne
What is tritrichomonas foetus
A very tiny parasite
Single celled organism
More complex than a bacteria or virus
lives in reproductive tract of cow and bull
3 long whip like projections
What treatments can you use for parasites
Need to be very specific about which drug you use - most drugs do not work in different classes of parasite
Avermectins
Benzimidazoles
Pyrethroids
others
Read the label or consult your vet
What did Dr John snow do for Infectious disease transmission
He was a medical doctor
He showed that the water companies drawing water from below the sewage outlet had more cholera cases - suggested water was what spread cholera (was thought it was bad air before)
Snow convinced the authorities after an outbreak, pump was disabled
snow is know recognized as the father of epidemiology
What are the lifecycle and midges of BTV
Adult midges are vectors, lifespan of adult midges is 20 days, adult midges killed by winter, midges overwinter as aquatic larvae, maximal duration of viremia in host is 63 days
Insect vector transmits virus during feeding -> virus replicates in primary vasculature and draining lymph node, transfer to sites of replication: lungs, lymph nodes and spleen, distributed by blood stream in association with red blood cells -> virus back to vector for onward transmission
What is epidemiology
The science concerned with the study of the causes distribution and control of diseases in populations
what is T foetus in bulls
Lives in the folds of the sheath and prepuce
Inhabits the microscopic crypts or crevices
bull are the long term carriers of the disease
They are usually infected for life
Older bulls are more likely to remain infected
What's the difference between infectious disease and contagious diseases
Infectious - any disease caused by an infectious organism
contagious - an infectious disease that spreads between animals
All contagious diseases are infectious, but not all infectious diseases are contagious
What are steps in the pathogen life cycle (hint 5)
Finding a host
Infection through the outer barrier and establishment in the host
Growth or multiplication of the pathogen inside the host
Reproduction, by exchange of genetic material between co-infecting strains
Development of transmission stages, and transmission to the next host
Pathogens can be transmitted through an intermediary such as a physical object
Fomite: any substance other than food that may harbour and transmit infectious agents - trucks (Foot and mouth), halters (ringworm), calf tube feeder & nipple bottles(salmonella), human hands (mastitis)
What are the 5 objectives of epidemiology
Determination of the origin of a disease whose cause is unknown
Investigation and conotrol of a disease whose cause is either unknown or poorly understood
Acquisition of information on the ecology and natural history of disease
Planning, monitoring and assessment of disease control programs
Assessment of the economic effects of a disease and analysis of the costs and benefits of control programs