Dr. James Evermann
Lecture 6: Infectious Organisms continued and Introduction
to Immunity
Viruses of:
Cattle Respiratory Viruses
The respiratory tract can be divided into the upper and lower tracts called:
the upper respiratory tract which includes the trachea to the point it branches
to bronchi. The bronchi and branches from the bronchi, called bronchioles, form
the lower respiratory tract.
- Infectious bovine rhinotracheitis (IBR, red nose) is primarily an upper respiratory
tract infection. Young calves between 2 and 6 weeks of age are affected.
Viral infections usually cause a serous nasal discharge. Serous means clear. This is in contrast to
bacteria such as Pasteurella, which usually cause purulent discharge.
Purulent means full of pus. Uncomplicated viral infections only cause serous
discharge from the eyes or nose. When the animal has a purulent discharge, then you know
they have a
secondary bacterial infection. When secondary bacterial infection
develops the infection often has descended into the lower respiratory tract.
- Parainfluenza type 3 (PI-3) PI-3 is also an upper respiratory tract infection and mimics
IBR very closely with signs occurring in 2 to 6 weeks. PI-3 infections are
usually uncomplicated.
- Bovine Respiratory Syncytial Virus (BRSV) causes a lower respiratory tract
infection. So you have to
question what killed the calf, lamb, or the kid, Pasteurellosis or the viral infection.
Upper respiratory infections may damage the cilia of the airways and allow
the infection to descend into the lower respiratory tract.
Gastrointestinal Viruses of Cattle
- Bovine viral diarrhea (BVD) causes diarrhea, usually in calves from 6 months to 8 months of age. Do you have any ideas why that particular age group?
The calf receives maternal antibody, or colostrum. Just about the time that
maternal BVD antibody weans the animals become infected and they show signs
of disease. Recall that maternal antibody is a form of passive immunity. For
comparison maternal antibodies against IBR and FDI3 last 4 to 6 weeks. Maternal antibodies protect
young animals for a certain period of time, then as maternal antibody
declines they become susceptible to disease. Calves become susceptible to
different viral disease at differing ages as maternal antibodies for
different disease last varying amounts of time.
- Rotavirus,
Coronavirus, and Torovirus are all classical GI only
viruses. They cause disease at 1 to 2 week’s of age. That is about the extent of
maternal antibody protection, 1 to 2 weeks. These viruses are spread in high
quantities in the feces. The dam infects the calf. These viruses "mow" the villi off in the small intestines.
IThe villi are necessary for absorption of nutrients and fluids. If
the villi are shortened by viral infection the calf loses water and
nutrients in diarrhea and rapidly loses weight.
Viruses of the Reproductive System of Cattle
- IBR
- BVD
- Bluetongue is a reproductive disease that causes congenital defects. These
animals maybe born without eyes, with hydrocephalus, cromedomes (large heads),
or without ears. IBR and BVD cause abortion.
Viruses of the Skin of Cattle
- Vesicular Stomatitis (VSD) is a reportable disease because it looks just like hoof
and mouth disease.
- Papular Stomatitis Also looks somewhat like vesicular stomatitis, but not
quite as severe. The lesions in the mouth are painful so the animals do not
eat well.
- Bovine papillomatosis are common warts, usually appearing on the skin of young calves between 3
to 18 months of age.
Sometimes warts spontaneously regress, other times they don’t. There has been some
discussion whether or not this is a zoonotic disease. As humans get papillomas as well.
The current feeling is that this is not zoonotic. Humans have their own
papillomas but they are not caused by the same virus that affects cattle
or horses.
- Bluetongue can cause skin irritations and a hypersensitivity to
sunlight. The lesions are crusty. Herefords are most often affected, usually on the white area of the skin,
as the lesions are caused by exposure to sunlight. The same thing happens to
affected sheep when they are recently sheered.
- Bovine mammilltis is an infection of the teats, occurring primarily in diary cattle.
It is
spread by milking machines. This is a nasty virus that affects the efficacy
of milking. A regular iodine teat dip will kill this
virus. Iodine is a very good disinfectant; not an antiviral, but a
disinfectant.
Nervous System Viruses of Cattle
- Pseudorabies means rabies-like. Pigs carry this virus. Cattle are a dead-end host. And when I
say dead-end, I literally mean dead-end; they die. You cannot distinguish this
disease from rabies. The animal starts circling, and head pressing,
then they go down, and start
paddling. If you see an animal with these signs you should notify a veterinarian
immediately. You may be dealing with pseudorabies, rabies, or BSE. BSE is exotic to the U.S.
- Rabies primarily comes from bats in the United States.
In other countries, such as Mexico, is carried by cats and dogs. In the U.S.
the dog population is well vaccinated against rabies. A sign in
cattle is that they stop eating. Lymph nodes in their neck swell and they cannot swallow, so they stop eating.
The veterinarian must open the mouth of the cow and stick their hand in to see if there is an
obstruction. You would be surprised at how many reports there have been of a
veterinarian sticking their arm in a cow's mouth and the animal has rabies.
We have had cases of rabies in horses, llamas, and of course unvaccinated dogs and cats. It
is estimated that about 10% of bats in the State of Washington carry rabies.
Retroviruses are in the same
family as HIV. These
viruses have RNA as their genetic type. They enter the host cell and what they do is quite
phenomenal. They convert themselves into viral DNA and then the viral DNA gets
incorporated into the animal's cellular DNA. Every time the infected cell divides, the virus divides.
Retroviruses persist
for the life of the animal. This is true for all retroviruses including HIV.
This is referred
to as latency. Latency is a silent infection. There are two retroviruses in
cattle.
- Bovine leukosis (BLV) is also called leukemia virus or bovine leukemia.
- The other is bovine lentivirus or
bovine immunodeficiency-like virus. Neither virus is zoonotic. They are spread in milk and
in the blood cells. When I say spread in the milk, I mean by infected cells
in the milk. Control for both of these diseases is to heat the milk. Also anything that spreads
blood between animals can transmit these. Dehorning equipment and needles
can transmit blood between animals. This is not a virus like IBR and BVD
that can be spread by a sneezing animal. This
virus is really difficult to spread. Unfortunately both the veterinarian
and the producer can be careless and transmit the virus between animals.
Control can be achieved by being more vigilant about sterilizing equipment between animals.
Pigs
Respiratory Viruses
- Swine influenza
- Porcine Respiratory and Reproductive Syndrome (PRRS)
Lactogenic immunity are antibodies in milk, but not colostrum. During the first 24 hours
after birth, immunoglobulins from colostrum are absorbed into the gut. So there
are two forms of gut immunity; colostrum (first 24 hours) and lactogenic
immunity (later). As a
result of early weaning the your animal can get an infection of the gut because
they do not receive lactogenic immunity. After about 24 hours the gut is
closed to uptake of immunoglobulins (antibodies). For the next two weeks
antibodies in the milk (lactogenic immunity) coat the surface of the gut and
protect the gut from E.coli and viral infections. Often producers will
milk-feed for the first 24 hours and then early wean the newborn.
- Transmissible gastroenteritis (TGE)
- Rotavirus
Reproductive Viruses of Pigs
- Pseudorabies causes abortion in sows.
- Parvovirus
- Porcine Reproductive and Respiratory Syndrome (PRRS)
- Porcine enteroviruses
- SMEDI complex. It means stillbirth,
mummified fetuses, embryonic death, and infertility. As a group these agents cause quite a
bit of damage in a sow operation.
Skin Viruses of Pigs
- Swine vesicular disease looks like VSD, but is not. However, it is still
reportable. Report any vesicular disease you see on a farm. Don’t try
and figure out what it might be, just report it and let the federal
veterinarian investigate.
- Vesicular exanthema is reportable because it is vesicular.
Nervous System Viruses of Pigs
- Pseudorabies can cause both neurologic signs and abortion in
the pig.
Respiratory Viruses of Horses*
(*Llamas, alpacas appear to be very susceptible to equine and bovine viruses)
- Equine influenza is primarily an upper respiratory tract infection. At about 2
years of age it becomes a lower respiratory tract infection. The horse can live with
the upper respiratory tract infection, no problems then all of a sudden it becomes it
becomes a lower respiratory tract infection. That is when you begin
vaccinating.
- Equine rhinopneumonitis (herpesvirus) causes inflammation of the nose and lungs. You have two of them. This is primarily from birth up until two years, primarily
upper respiratory tract infection. There are two viruses causing respiratory
signs equine herpes 1
and 4; one in young horses less than 2 years old followed by the equine influenza at two years of age.
The gastrointestinal viruses of horses are the same viruses that
affected other species. When you see a foal with diarrhea the foal may have a failure of passive transfer, or worse
yet may have combined immunodeficiency (CID). The mare protects her foal with maternal antibody; however, if
the foal develops and infection it is usually a clue that there is failure
of passive transfer or they have some kind of immune deficiency syndrome.
- Rotavirus
- Coronavirus
- Torovirus
Reproductive Viruses of Horses
- Equine Herpes Virus 1 (EHV-1)
- Equine Herpes Virus 4 (EHV-4)
- Equine coital exanthema This is a true venereal disease. The male carries the virus.
Usually he is subclinical. He infects a mare and she gets vaginitis. This infection does not cause
abortion, but it looks very
similar to herpes equine 1 and 4, which do cause abortion. This is a problem
that you want to try and
find out what is happening as soon as possible.
- Equine viral arteritis (EVA) is also a venereal infection. It is
transmitted by
stallions with infected semen. Stallions are usually subclinical carriers. The outcome is abortion.
Skin Viruses of Horses
- Horses may also acquire vesicular stomatitis. Cattle and horses are both susceptible to this.
- Equine papillomatosis causes warts. This virus is similar to the in bovine
papillomatosis viruses, but is not the same.
Nervous system Viruses of Horses
- There are three equine encephalitis viruses; western, eastern, and Venezuelan.
The distribution of the viruses is western U.S., eastern U.S., and South America. The virus is in the
blood and is spread by mosquitoes.
- Rabies
Retrovirus
- Equine infectious anemia EAI is also called swamp fever. This test is required pre-sale or pre-shipment across state borders. This is a
required regulatory test.
Respiratory Viruses of Sheep and Goats
These are the same viruses that
affect cows.
- Infectious bovine rhinotracheitis (IBR)
- Parainfluenza type 3 (PI-3)
- Bovine Respiratory Syncytial Virus (RSV)
- Adenovirus causes an
upper respiratory tract infection that progresses to pneumonia. The virus
predisposes to a secondary infection with Pasteurella. Sheep and goats are
very susceptible to Pasteurella.
Gastrointestinal Viruses of Sheep and Goats
- Rotavirus is similar to the one in cows, primarily affecting lambs and kids up to about 4
weeks of age.
Reproductive Viruses of Sheep and Goats. These viruses cause abortion and birth
defects referred to as congenital defects.
- Border disease: The name derives from Europe, actually between the borders of Scotland
and England. This is also referred to as Hairy Shaker disease. At birth the
lamb's wool looks like hair because the virus has affected the hair follicles. These animals usually do not have a thymus.
The thymus is located deep in the neck area and
is the origin of the T-cells. An animal that doesn’t have a thymus doesn’t live very long. These animals usually die between
1-2 weeks of age.
- Cache Valley occurs primarily in Utah and causes abortion and birth
defects primarily in sheep.
Skin Viruses of Sheep and Goats
- Bluetongue (BTV) causes aspiration pneumonia in sheep. The esophagus starts to swell and they can’t breathe very well, so
they start gulping. They will inhale some of the ingesta. That material gets
into the lungs and causes aspiration. They don’t die directly from bluetongue, they
die of aspiration pneumonia.
- Orf-Contagious ecthyma: Like cattle, the sheep become photosensitized. The
disease occurs in lambs or
sheep recently sheered. They don’t have wool protecting their skin they
develop an intense sunburn. Orf is the common name. This is a pox-virus. Scabs
from affected sheep drop off, get into the soil, and remain infective for years.
The lesions on lambs or goat kids occur around the muzzle and look like a massive
scab. The muzzle lesions interfere with
eating. The disease usually doesn’t go any further than that. Usually it is not fatal.
The disease is zoonotic. If you handle infected sheep and goats and you have any sores
on exposed skin and you touch the scabs, the virus can enter the sore.
The affected body pare (e.g. hand, face, etc) will swell. Your lymph
nodes swell. It is rather severe and incapacitates you for about two weeks. It is not
fatal, but is really painful. If you see animals with scabs around the muzzle,
put on gloves. This is the safest way to prevent you from getting the
disease.
Nervous System Viruses of Sheep and Goats
Retrovirus
- Sheep and goats have two retroviruses;
one is referred to as ovine progressive pneumonia abbreviated OPP. The virus
is acquired from ewe’s milk. The incubation period, which is the time between infection
to disease, can be anywhere from 3 months to 3 years. This is a long incubation
period. As the name implies the animal develops pneumonia, labored breathing, and
wastes away.
- Caprine Arthritis Encephalitis (CAE): manifests as two syndromes; brain lesions in goat kids at less than
6 weeks of age and arthritis is older goats. It is 100% fatal in kids. This is similar
to OPP in sheep. The incubation period is between 3 months and 3 years. The
goat's knees become enlarged and hard. They are are not warm and soft
like inflamed knees. This is a common feature of CAE virus in goats.
Prions
Bovine spongiform encephalopathy (BSE) BSE is a prion disease. It is thought
to have originated from sheep. BSE is very strongly implicated in human Crutzfelt-Jacob disease.
Since August 1997, no sheep or goat material is used as a protein source for cattle in the United States.
Bacterial infections: You can differentiate a viral infection from a bacterial
infection by the type of discharge present. Viruses usually are responsible when there is a clear serous discharge. Bacteria have a tendency to
cause a mucopurulent discharge; (pus filled discharge). The bacteria live in the
mouth and can act as opportunistic pathogens. Given the opportunity, bacteria
can move from the mouth to the upper respiratory tract and then move into the
lower respiratory tract. Growth in abnormal locations is called colonization.
Bacteria can be cultured several ways. Trans-tracheal wash is a procedure in
which sterile fluid is flushed into the airways then suctioned back up. A sample of
the fluid is plated on series of synthetic media, such as a raw agar plate. The
bacteria grow in colonies on the agar. This is a major hallmark of bacteria; they can grow on synthetic
media; viruses cannot. You can clearly identify Pasteurella bacteria
from Haemophilus bacteria just based on its colony morphology.
Bacteria are either gram positive and gram
negative. Gram-positive bacteria stain blue. The reason they stain purple or blue
is that they have a very thick cell wall. Gram-negative bacteria stain either red or pink.
Gram negative bacteria have a high lipid (fatty acid) content in the cell wall. An example of
a gram negative bacteria is E. coli. An example of a gram positive bacteria is clostridia.
FAQ
Question: Is it safe for other animals to ingest the meat from a BSE
positive animal?
Dr. Evermann: The carcass must be removed from the pet food chain, too. At Washington
State University we cannot render any goat or sheep material. It
has to be incinerated. This varies with the locale. This is a good
question because cats are susceptible to prion diseases. They haven’t shown
up in
dogs yet. That doesn’t mean they are not susceptible. It was
discovered that cats develop prion disease, as zoo cats (lions, tigers, and
cheetahs) fed cut up carcasses of sheep, goats and cattle
with BSE came down with what looks like
a bovine spongiform encephalopathy.
Question: If an infection causes the intestinal mucosa to
slough off is the gut epithelium able to replace itself?
Dr. Evermann: Yes, if it is not too severe. You may have seen
calves that appear close to death and if you give them some fluids, and they bounce back.
last edited by crd January 20, 2000