Zoonotic risk and production loss of toxoplasmosis in ruminants

04/02/2023

14/10/2022

Sulfonamides are used to treat toxoplasmosis in goats. Clindamycin (12.5 mg/kg, IM, BID for 3 weeks) is also recommended. There is no vaccine available in the U.S. for toxoplasmosis.
Many of these drugs are not licensed for use in goats and may only be used on the advice of a veterinarian. Good management practices can also help control toxoplasmosis. Pregnant females should not be exposed to infected cat f***s so it may be necessary to limit the cat population in the barn where pregnant doe/ewes are housed or feed is stored.

14/10/2022

Toxoplasmosis results from infection of susceptible sheep with the protozoan parasite Toxoplasma gondii. The s*xual cycle takes place in cats while the as*xual cycle can occur in a range of species including sheep. Infection during early pregnancy may be manifest as embryo/early fetal loss with an increased number of returns to service after an irregular extended interval or an increased barren rate, often above 8 to 10 per cent. Often the highest number of barren sheep is in the youngest age group. Toxoplasma infection during mid pregnancy results in abortion or production of weakly live lambs near term often with a small and leathery mummified fetus.

14/10/2022

Control
Control of toxoplasmosis is based on three equally important aspects:
Retaining sheep in the flock after an abortion episode – Sheep that have aborted with toxoplasmosis are immune, probably for life. It is therefore important to retain as many sheep in the flock that were exposed to disease as possible after the outbreak as these sheep will maintain a high level of flock immunity, meaning that only replacements will have to be vaccinated.
Rodent control – As rodents provide an ongoing source of infection, an effective rodent control plan must be implemented on farm. This includes maintaining the farm cat population as part of this process. However, it is useful to neuter all farm cats to avoid the production of further kittens that can act as a new source of infection. Euthanasing existing farm cats is not a useful approach as this often leads to the entry of a new population of cats, providing further kittens which will potentiate the infection and life cycle of disease
Vaccination – A live vaccine, Toxovax, is available for the control of toxoplasmosis. The vaccine is administered at least 3 weeks ahead of tupping and must be ordered specially in advance as it has a short shelf-life. It is advisable to keep in close contact with your prescribing vet and collect the product as soon as it arrives with them. Use the product on the day of collection from your vet. Once toxoplasmosis has been diagnosed on a farm, vaccination ahead of the next tupping is only conducted in replacement sheep. The only exception to this is if various groups are maintained separately on a farm where exposure levels to toxoplasmosis vary between groups. This can lead to variable levels of immunity and in that circumstance it may be advisable to vaccinate all sheep in non-exposed groups to avoid future losses, particularly if sheep move between groups where their exposure status could change. For information on the vaccine please click here. Further information is available from your local veterinary practitioner from whom advice must be sought.

14/10/2022

Clinical Signs
There are five main syndromes of abortion in sheep – Barren to tup, abortion, mummification (particularly common with toxoplasmosis), stillbirth (occasionally one live lamb born with a dead lamb) or the birth of weak lambs which fail to suckle properly and often succumb to disease in young life. It is however common to have many or all of these syndromes on a farm at the same time.
A clinical sign which is characteristic of toxoplasmosis abortion is the development of small white areas in the cotyledons (buttons) of the placenta. These are caused by focal necrosis (death of cells) in areas of the placenta due to damage caused by multiplication of the Toxoplasma organism.

14/10/2022

Epidemiology
The clinical consequences of infection are determined by the timing of infection, the immune resistance of the animal infected and the numbers of toxoplasma oocysts taken in. Toxoplasmosis is caused by toxoplasma oocysts picked up from feed or hay, or off pasture that has been contaminated by cat faeces. Toxoplasma oocysts are shed by cats for a short period when they have just been weaned and first start hunting. This is because the cat becomes infected by eating infected rodents. One adolescent cat can shed enough cysts to infect thousands of ewes. This is because infection of a few oocysts from an infected mouse are amplified in the cat through massive multiplication resulting in shedding of millions of oocysts in the cat’s faeces over a few weeks, after which the cat becomes immune. These oocysts are very resilient and can survive for very long periods in feed or on pasture. The organism also survives from generation to generation in mice and rats providing an ongoing source of disease for susceptible cats. It is important to realise that toxoplasmosis is NOT a sheep to sheep disease so mixing sheep prior to pregnancy will not result in control.
Once a ewe has been infected, she soon becomes immune and is unlikely to show signs of the disease in subsequent years. It is only when an infection is picked up for the first time during pregnancy that problems occur.
The stage at which an infection is picked up during pregnancy will determine the outcome as there is an approximate six week lag period between infection and onset of clinical signs:
First 60 days – foetus absorbed and the ewe appears barren.
60 – 120 days – abortion in late pregnancy with mummified foetuses, stillbirths or weak and sickly lambs that often die.

14/10/2022

Aetiology
Toxoplasmosis is caused by Toxoplasma gondii, a protozoan parasite. This microscopic organism causes infection in a variety of species though the main source of infection is cats.

14/10/2022

Toxoplasmosis is a disease caused by a protozoan parasite. The main source of infection is cat faeces. If you encounter a sheep abortion episode it is important to establish a definitive diagnosis as there are quite a number of causal agents that contribute to the abortion syndrome. Toxoplasmosis is not restricted to sheep. The disease is zoonotic, which means it can be passed to humans. In humans it can cause acute, life-threatening illness, and infection of a pregnant woman could seriously damage her unborn child. Pregnant women should avoid all involvement with lambing ewes and shouldn’t even handle the clothing of those who work with sheep.

05/10/2022

05/10/2022

Diagnosis
Diagnosis of toxoplasmosis is usually based on identification of specific changes in the placenta in combination with the detection of high levels of antibodies in ewe blood. Antibody may also be present in the fetal fluids and can also be detected in newborn lambs before they have sucked colostrum. Blood sampling of the ewe alone is not sufficient as a positive result merely indicates past infection not that the current abortion is due to toxoplasmosis.

05/10/2022

Management/Prevention/Control measures
All sheep feed should be stored in vermin-proof facilities to prevent contamination by cats and other vermin. Vaccination provides excellent immunity to natural infection and should be administered at least three weeks before the breeding season. Care should be taken when administering the vaccine; the detailed safety instructions provided by the manufacturer should be followed closely

05/10/2022

Toxoplasmosis, caused by Toxoplasma gondii, infects humans by consuming infected raw or undercooked meat and foods harboring mature oocysts. In this study, we assessed the prevalence of T. gondii in sheep and goats coming from central Iran. After completing the questionnaire, about one gram of liver or diaphragm tissue was taken as a sample from 90 sheep and 90 goats slaughtered in Yazd Province and stored at – 20 ºC. DNA extraction was done, and then T. gondii was detected using nested PCR.
slaughtered animals was 11.6% (21 of 180), including 14.4% (13/90) in sheep and 8.8% (8/90) in goats. The infection rates in liver and diaphragm samples were 12.2% (11/90) and 11.1% (10/90), respectively (p = 0.8163). The infection rate in animals older than one was 16.3% (15/92), and it was 6.8% (6/88) in animals under one year of age. Therefore, no significant differences were found (p = 0.475). Infection rates were 19.5% (18/92) in males and 3.4% (3/88) in females (p = 0.0007). In conclusion, the infection rates of toxoplasmosis in livestock in this area are almost high, and therefore, it is necessary to design appropriate prevention programs to control the disease.

05/10/2022

Vaccines against T. gondii in sheep and goats and the associated immune response
Different types of available vaccines against T. gondii in sheep and goats and their characteristics are summarized in and detail of these vaccines and the immune responses induced in vaccinated animals

05/10/2022

Clinical Findings of Toxoplasmosis in Animals
The tachyzoite is the stage responsible for tissue damage in toxoplasmosis; therefore, clinical signs depend on the affected tissue, the number of tachyzoites released, and the ability of the host immune system to limit replication and transmission. Because adult immunocompetent animals control tachyzoite transmission efficiently, toxoplasmosis is usually a subclinical illness. However, in susceptible species, as well as in young and immunocompromised animals (particularly puppies, kittens, and piglets), tachyzoites are transmitted systemically and cause interstitial pneumonia, myocarditis, hepatic necrosis, meningoencephalomyelitis, chorioretinitis, lymphadenopathy, and myositis. The corresponding clinical signs include fever, diarrhea, cough, dyspnea, icterus, seizures, and death.
T gondii is also an important cause of abortion and stillbirth in sheep, goats, cervids, and sometimes pigs. After infection of a pregnant ewe, tachyzoites are transmitted via the bloodstream to placental cotyledons, causing necrosis. Tachyzoites may also be transmitted to the fetus, causing necrosis in multiple organs. Finally, immunocompromised adult animals (eg, cats infected with feline immunodeficiency virus) are extremely susceptible to developing acute generalized toxoplasmosis, mainly expressed as neurologic and respiratory disorders.
Women who acquire T gondii during pregnancy can develop a fever, and transplacental passage of tachyzoites to the fetus may occur. Veterinarians have a key role in preventing this zoonotic disease by recognizing contamination of the environment and water by oocysts, by observing the presence of cysts in animal tissues, and by helping to develop, disseminate, and apply control measures.

05/10/2022

Many of you may have heard of Toxoplasmosis and it’s relationship to pregnant women. I know as a small animal practitioner, I get many calls from pregnant women who are wondering if they need to get rid of their cat. Here is the scoop… Toxoplasma is protozoan parasite that is carried by rodents and birds. Cats are infected when they eat the mouse or bird and then the Toxo organism will live part of its life cycle in the cat. The organism is passed in the cat f***s and then must sit in the environment for a couple of days before it becomes infective to people or to our goats. (In other words, you could eat fresh cat p**p and NOT get sick, the stool must be OLD to be infectious! This is a key point.) Once cats become infected with Toxo they will always have it, but they will only pass it in the stool for a brief time just after they are first infected. Most cats only pass the organism in the stool ONCE in their lives and usually when they are kittens. The exception to this would be if an older cat got another disease that suppressed their immune system (such as feline leukemia or feline aids).

When kittens that are shedding the organism defecate in the hay, feed bins, or bedding, the goats can potentially become infected. People get infected when cats bury their stool in the garden and people work in the garden without gloves or face masks…yes you can actually get this by breathing the dust that is carrying the parasites. Goats can also get it this way. Another way you can get the organisms is by eating meat that contains the parasites. When goats, cows, pigs or other animals are infected by the parasite, they (the organisms) don’t really know what to do so they swim around in the animal’s body and form little “cysts” in the muscle tissues. When you eat the cysts in the muscle, you can get Toxo. What most folks are concerned with is cleaning the litter box, but if this is done daily the p**p will be fresh and the organisms will not be infective yet.

So what is the big deal? Well….Toxo is one little bug that can cause big, big problems. People that are not pregnant and that have good immune systems generally just get slight flu like symptoms and don’t even know it was the bug. It doesn’t really go away, it goes to your brain tissue and some in your muscle tissue and just sits there for years. If you get AIDS or Cancer and are immunosuppressed for some reason, the little critters can come out of their “cysts” and cause severe problems or even death. The biggest problem is in pregnant women or young children with immature immune systems. The organism will infect unborn babies and cause severe birth defects or miscarriages. It can get into the retina of the eyes and cause blindness or it can get into the brain and cause neurologic disease in children.

So why are we concerned with it in goats? It does many of the same things as it does to people! If the doe gets infected while she is pregnant, the organism can multiply in the placenta and infect the fetus. This can cause miscarriages and stillbirths, weak kids and kids with neurologic disease. Occasionally, but not often, the infected doe will run a fever, but most show no clinical signs other than abortion. If the doe has a bad immune system she may develop a neurological form of the disease. Is there another reason we worry about this in goats? Yes—infectious organisms can be passed in the milk and will also be in the muscle of the goat. As I said earlier, adults that have a good immune system could get infected by drinking the milk but they will show no or only very mild signs of a problem. However, infants or immune compromised people that drink infected goat milk could come down with very severe disease. Pasteurization or boiling of the milk will kill the organism. Goat meat that is infected could also infect a human and that is one reason to cook your meat until the juices run clear. Meat does not have to be well done but the juices must not be pink or red, they must be clear.

How can we diagnosis this? Because most adult does do not show symptoms it is hard to diagnose it in the adult animal. Diagnosis is most reliable if the aborted fetus and the placenta are sent to the lab. If your doe aborts, do NOT let her eat the placenta and do NOT throw it away. The placenta is the key to diagnosing many causes of abortion (not just toxoplasma.) Wrap everything up, including the aborted fetus, and put it in a plastic bag in a refrigerator. Most of the time it can actually be frozen but not always. Until your vet examines the tissues and determines which tests need to be run, it is best to refrigerate. Remember, you cannot refrigerate it forever without the tissue breaking down. Examination and laboratory analysis need to be done within 2-3 days maximum. Blood tests can be run on a weak kid but the blood must be drawn BEFORE the kid gets colostrum. Antibodies may be passed from the doe to the kid in the colostrum that would make the test positive. These antibodies would be present in the doe if she had ever in her life been infected. If she was infected BEFORE the pregnancy the Toxo will not cause a problem. The problem is only if she is infected during the pregnancy. Therefore, antibodies passed to the kid will show in blood tests but do NOT mean that Toxo was the problem.

How do we prevent this? That is a tough problem. Many folks recommend getting rid of your barn cats. The problem is that stray cats passing through your barn or pasture can also shed the organism. Other people have advocated having a few, neutered barn cats. These cats are not going to be having kittens (the age most likely to shed the parasite) and they are going to hopefully chase off any stray cats that come around. The most successful method of preventing this is to keep the feed and the hay in areas where cats cannot get to it. Cover your hay feeders and keep the hay off the ground. Keep feed in closed containers. Clean any hay or feed that could potentially have cat f***s in it daily. (Remember-fresh f***s is not a problem, the organism cannot infect you or your goats unless it has sat in the environment for a couple of days.) Even this method is difficult and we all need to be on the lookout for signs of a problem.

05/10/2022

If toxoplasmosis is the cause of abortion in a herd, a veterinarian should be consulted. Feeding decoquinate (2 mg/kg bw/day) or monensin (15-30 mg/head/day) throughout pregnancy may reduce the abortion rate in a herd with a history of toxoplasmosis. Sulfonamides are used to treat toxoplasmosis in goats. Clindamycin (12.5 mg/kg, IM, BID for 3 weeks) is also recommended. There is no vaccine available in the U.S. for toxoplasmosis.
Many of these drugs are not licensed for use in goats and may only be used on the advice of a veterinarian. Good management practices can also help control toxoplasmosis. Pregnant females should not be exposed to infected cat f***s so it may be necessary to limit the cat population in the barn where pregnant doe/ewes are housed or feed is stored.

05/10/2022

Toxoplasmosis
The main problem in goats affected by this organism is abortions. The organism is a protozoan called Toxoplasma gondii. Toxoplasma is a one-celled parasite. It is more of a problem in sheep and is a major cause of abortion, mummification, stillbirth, and weak kids. Cats are the carrier of the organism. They become infected by eating uncooked meat scraps, placentas, and small rodents. Recently infected cats then shed the eggs in their f***s. Goats become infected by eating grass, hay, or grain contaminated by cat f***s. It reaches the reproductive tract by the blood after invasion of the small intestine. If the goat is pregnant at the time of initial infection, Toxoplasma commonly invades the placenta and fetus approximately two weeks after initial infection of the doe. Fetuses infected in the first half of pregnancy are more apt to die than fetuses infected in the second half. Previously infected goats are usually resistant to abortion when challenged again by the organism. Symptoms are aborted fetuses, typically in the first half of pregnancy. The definitive diagnosis is made using laboratory analysis based on serology or histology. There is no effective treatment recognized for toxoplasmosis at this time. Control is based on sound sanitation and best management practices. Steps should be taken to prevent exposure of susceptible goats to the eggs in cat f***s during pregnancy. Store grain and feed in covered containers. Keep a closed herd of cats on the premises. Spay and neuter cat populations. Do not feed raw meat to cats. Dispose of aborted fetuses and placentas in acceptable manners. Wear protective gloves when handling infected material and pasteurize milk and properly cook meat fed to cats. This organism is contagious to humans, and pregnant women should be careful when handling cat f***s and contaminated aborted material. Vaccination is available.

19/08/2022

19/08/2022

Treatment
Treatment usually involves a course of an antibiotic called clindamycin, either alone or in combination with corticosteroids if there is significant inflammation of the eyes or central nervous system. Treatment should ideally be started immediately after diagnosis and continued for several days after signs have disappeared. In acute illness, treatment is often started on the basis of high initial IgM antibody levels. If clinical improvement is not seen within two to three days, the diagnosis of toxoplasmosis may be questioned.
Prognosis
The prognosis for cats diagnosed with toxoplasmosis depends upon the organs or systems affected, the time between infection and treatment, and initial responses to therapy. Generally, cats with CNS and eye symptoms respond to therapy more slowly, but they still have more favorable prognoses if their clinical signs improve within 2-3 days of starting therapy. The prognosis for cats with toxoplasmosis affecting the liver or lungs is usually poor.
Prevention
Reducing the incidence of toxoplasmosis in cats requires measures to reduce both exposure to infective oocysts and shedding of oocysts into the environment. Cats should preferably be fed commercially prepared, cooked foods (appropriate heating inactivates any T. gondii cysts that may be present) and should not be allowed to eat uncooked meat or intermediate hosts, such as rodents. They should also be denied access to facilities housing food-producing livestock and food storage areas.
Because cats only shed the organism for a short time, the chance of human exposure via cats they live with is relatively small. Owning a cat does not mean you will be infected with Toxoplasma. Since it takes a minimum of 24 hours for T. gondii oocysts in cat f***s to sporulate and become infective, frequent removal of f***s from the litter box, while wearing gloves and washing hands afterward, minimizes the possibility of infection. It is unlikely that you would be exposed to the parasite by touching an infected cat, because they usually do not carry the parasite on their fur. It is also unlikely that you would become infected through cat bites or scratches. Indoor cats that do not hunt prey or consume raw meat are unlikely to be infected with T. gondii. In the U.S., people are much more likely to become infected by eating raw meat and unwashed fruits and vegetables than by handling cat f***s. The possibility of infection after gardening in soil that has been contaminated with cat f***s also exists, and this possibility can be mitigated by wearing gloves and by washing hands after gardening.
Pregnant women and immunodeficient individuals are the two populations most at risk of developing health problems after T. gondii exposure. In utero infection is of the greatest concern in humans. Between one-third and one-half of infants born to mothers who acquired Toxoplasma during pregnancy are infected. The vast majority of women infected during pregnancy have no symptoms themselves, and the majority of infected infants will show no symptoms of toxoplasmosis at birth. Many of these children, however, are likely to develop signs of infection later in life, including loss of vision and hearing, mental retardation, and, in severe cases, death.
In people who are either undergoing immunosuppressive therapy or have an immunosuppressive disease such as acquired immunodeficiency syndrome (AIDS), toxoplasmosis may cause enlargement of the lymph nodes, eye and central nervous system disturbances, respiratory disease, and heart disease. In these patients, especially those with AIDS, relapses of the disease are common, and the mortality rate is high.
Toxoplasmosis begins its life in the stomach of the cat, which is also the only place it can reproduce so its mission once expelled is to find its way back in there. The bizarre path it has adapted goes via rats, who eat cat f***s and become infected. Usually, a rat will steer well clear of a cat, running at even the faint whiff of their urine. A toxo rat, however, suddenly finds the stuff delectable and will seek it out, increasing its chances of ending up in the stomach of the cat and taking the toxo with it. Clever parasite.
So how does it do it? It takes around six weeks after munching on some infected cat f***s for toxoplasmosis to get to the brain, where it forms cysts in the amygdala region. Here, it shrivels dendritic nerve cell endings linked to neural pathways that govern the rat’s response to predation. At the same time, the toxo also works away to rewire the area of the brain in charge of s*xual attraction and effectively links together the two paths. Now, rather than smelling urine and feeling fear, the rat smells urine and feels… frisky. The crossover sees the randy rat actively seeking out cat urine and soon, the toxo is right back where it wanted to be.
For all its ingenuity, toxoplasmosis is going to have a tougher time trying to get the body of a human into the stomach of a cat, and if you’re wondering how infected patients feel about cat p**s I’m delighted to inform you that this study tried to find out exactly that by doing precisely what you expect. They rounded up 34 toxoplasma-infected and 134 non-infected students to sniff wee samples from a cat, horse, tiger, brown hyena, and dog and rate them on their intensity and pleasantness. The sniffers didn’t know if they were infected or not, nor which species the p*e-perfumes were from. Olfactory function wasn’t found to differ between participants, but there was a strong, s*x-dependent effect of toxoplasmosis on the pleasantness attributed to cat urine. Infected men liked the cat p*e more than noninfected men, yet there was no difference between infected and non-infected women in their perception of the p**s. Not a sentence I thought I would be writing this week.

19/08/2022

Diagnosis
Toxoplasmosis is usually diagnosed based on a cat’s history, signs of illness, and laboratory test results. Measurement of two types of antibodies to T. gondii in the blood, IgG and IgM, can help diagnose toxoplasmosis. High levels of IgG antibodies to T. gondii in a healthy cat suggest that the cat has been previously infected and is most likely immune to the organism and not excreting oocysts. These cats are no longer sources of infection for other hosts. High IgM antibody levels, in contrast, suggest an active infection. The absence of any T. gondii antibodies in a healthy cat suggests that the cat is susceptible to infection and would shed oocysts for up to two weeks following infection.
The detection of oocysts in the f***s is not a reliable method of diagnosis because they look similar to those of some other parasites. Additionally, cats can also shed oocysts for only a short period of time and often are not shedding oocysts when they are showing signs of disease. A definitive diagnosis requires microscopic examination of tissue samples for distinctive changes to the tissues and the presence of tachyzoites.

19/08/2022

The most common symptoms of toxoplasmosis include fever, loss of appetite, and lethargy. Other symptoms may occur depending upon whether the infection is acute or chronic, and the location of the parasite in the body. In the lungs, T. gondii infection can lead to pneumonia, which will cause difficulty breathing that gradually worsens. Infections affecting the liver may cause a yellowish tinge to the skin and mucous membranes (jaundice). Toxoplasmosis can also affect the eyes and central nervous system (CNS), producing inflammation of the uvea, or pigmented part of the eye (uveitis), the retina, or the space between the lens and cornea (the anterior chamber) abnormal pupil size and responsiveness to light, blindness, lack of coordination, heightened sensitivity to touch, personality changes, circling, head pressing, ear twitching, difficulty chewing and swallowing food, seizures, and loss of control over urination and defecation.

19/08/2022

Clinical Signs
Most cats infected with T. gondii show no signs of disease. Occasionally, however, a clinical disease called toxoplasmosis occurs, often when the cat’s immune response cannot stop the spread of tachyzoite forms. The disease is more likely to occur in cats with suppressed immune systems, including young kittens and cats with feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV).

19/08/2022

Other animals, including humans, are intermediate hosts of T. gondii and can become infected by eating cysts or oocysts. Oocysts passed in the f***s of cats are not immediately infectious to other animals. Before becoming infectious, they must go through a process called sporulation, which takes one to five days depending on environmental conditions. Cat f***s containing sporulated oocysts, however, serve as sources of infection, regardless of whether they are in litter boxes, gardens, or in sand boxes in which outdoor cats have defecated. Once an intermediate host ingests sporulated oocysts, the infection results in the formation of tissue cysts in various tissues of the body. Tissue cysts remain in the intermediate host for life and are infectious to cats, people, and other intermediate hosts that eat the cyst-containing tissue. In some cases, T. gondii tachyzoites may be excreted in the milk of infected cows and goats. See Figure 1 for an illustration of the life cycle of T. gondii.

19/08/2022

The life cycle of T. gondii is complex and involves two types of hosts — “definitive” hosts in which the parasite reproduces and forms eggs (called oocysts), and “intermediate” hosts in which it reproduces by making clones of itself, which cluster inside cysts. Wild and domestic cats are the only definitive hosts for T. gondii. When a cat ingests infected prey or raw meat, the parasite is released from cysts into the cat’s digestive tract, where it reproduces and produces oocysts. Infected cats then excrete these oocysts in their f***s by the millions. Newly exposed cats usually begin shedding oocysts three to 10 days after consuming infected tissue, and continue shedding for around 10 to 14 days. Oocysts are very hardy and may survive in the environment for well over a year. Additionally, some of the T. gondii released from cysts from the infected meat will pe*****te more deeply into the wall of the cat’s intestine and multiply as yet another form, called a tachyzoite. This form then spreads from the intestine to other parts of the cat. Eventually, the cat’s immune system forces the parasite into a dormant or “resting” stage
where it forms cysts in muscles and the brain. These cysts contain slowly multiplying Toxoplasma organisms in yet another form, called a bradyzoite.