Multifactoral Flashcards
What is a multifactoral disorder
many genes and environmental triggers
accounts for the vast majority if late onset inherited diseases
sporadic occurance in pedigree
incidence not equal between sexes
difficult to eradicate
what is canine malignant lymphoma
triggered by 2,4-D herbicide (weed and feed)
exposure 3-5 days after application, via grooming
cancer
diabetes in dogs
2-5 females and 1 male
gender imbalance
exacerbated by pregnancy
what does multifactoral cause in hereford cattle?
cancer eye
lack of pigmentation and is worse from sunlight
Osteochondrosis
effects dogs, pigs, horses - more males then females
pitted ball joint - femur/humerus
exacerbated by rapid weight gain (gender imbalance)
Hip Dysplasia
shallow acetabulum
more severe cases shown in younger ages
occurs in most large dog breeds
increased age increase arthritis increasing pain
what are possible environmental triggers for hip dysplasia?
rapid growth (overfeeding)
dietary imbalance
over exxercise
what is epilepsy
multifactoral seizure disorder
more common in certain breeds, such as belgian shepards
polygenid trait caused by stress and sex hormones
indicatorars of multifactoral inheritance
late onset
sporatic occurance in pedigree
incidence not equal between sexes
how do you calculate risks
its the sqaure root of incidence
this risk rises every first relative parent, sibling and offspring
5% 1 parent or sib or offspring
10% 1 parent and 1 sib
20% 1 parent and 2 siblings
how does risk of reoccurance increase
more severe the case or the earliier the onset
mating is consanguineous
trigger is common
multiple family memebers affected
what is the burden of disease
- severity of symptoms
- cost of treatment
- pain or discomfort
how do you make breeding decisions
client must weigh risk and burden
5% risk of eye cancer … but about 50% of the carcass is then condemned
5% risk of hip dysplasia
What is the genetic advice for breeding decisions
avoid repeat matings that produce multifactorial diseased offspring
suggest healthy lifestyle changes in breeds known to be susceptable
what are the goals of future breeding programs
- fewer antibiotics used, especially in meat producing animals
- greater longevity
- increased quality of life/health
- increased milk production (peaks at 4-5 years of age in dairy cattle)
what is teratogenesis ?
abnormal development influenced by drugs, viruses, chemicals, radiation - in utero = mammalian phenomenon
examples of teratogenesis?
twisted legs(cattle)
cyclopean(lambs)
cleft palate(cattle, dogs)
heart defects (sheep)
what is the biological threshold?
developmental processes occur on a fixed schedule
at a fixed period in gestation, disruptions or delays cause that organ to be incompletely developed
what are spina bifida risks?
maternal folic acid deficiency
exposure to high temperature in early pregnancy (prolonged fever or hot tub use)
maternal insulin-dependednt diabetes
medications (anti-seizure)
what is a cleft lip and palate
in utero development of face at 7-9 weeks (cattle)
fixed time period for facial development
delay (fever, virus)
face not finished (failt fusion of nasal processes )
what is important in tereatogenesis?
genetic backgroun (predisposition to the tetratogen, predisposition to the malformation)
exposure (time and length, dose)
generalizations of teratogens
- animal pregnant or lactating at time of exposure (rarely through male)
- few effects last prior to conception
- most effects have a two week delay
preimplantation a safe period or embryo dies - primarily congenital defects
What is the development stage at time of exposure
stage = effect
blastocyst = lethality
organogenesis = structureal defects
histogenesis = microscopic changes
growth = stunting
what are types of direct acess for teratogens
radiation, microwaves, ultrasound
