The study of parasites is called parasitology. It is an important discipline because internal parasites cause death and disease worth billions of dollars in animals each year. These parasites have highly evolved life cycles that make their elimination impossible. In addition, many internal parasites affect people with the potential for serious consequences.
Dogs and cats (especially puppies and kittens) are routinely infected with internal parasites, sometimes without apparent evidence of the infestation until it is too late. This means that a pet can have internal parasites even though the fecal sample is negative. Fortunately, we have effective medications to treat most parasites.
Many of the medications we use to treat internal parasites, called anthelmintics, treat more than one parasite. The advent of these broad spectrum anthelminitcs makes treatment much more effective. We recommend all dogs and cats get a treatment for internal parasites every 6 months.
This section will discuss internal parasites that are commonly found in dogs and cats in our area. These internal parasites differ from external parasites, which usually affect the skin and ears of dogs and cats. Click here to learn more about external parasites.
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Symptoms manifested by pets that are infected with internal parasites can vary, and depend on a pet's age, nutritional status, parasite load, duration of infestation, etc. One of the most common symptoms of internal parasitism is diarrhea. Other symptoms include poor appetite, lethargy, coughing, and abdominal distention.
Some pets don't show any symptoms while others can die from their infestation. Internal parasites tend to infest older and younger animals most commonly. Internal parasites can also make a pet more susceptible to other diseases. It is not uncommon for a puppy with Parvo virus to have internal parasites simultaneously.
Due to the prevalence of internal parasites in dogs and cats, their lack of symptoms in some cases, and the potential for humans to become infested also, your pets feces should be checked for internal parasites twice a year. Dogs and cats that are outside and exposed to other animals should have their feces checked more often.Routine worming should be performed on all dogs and cats every 6 months, even if the stool check for parasites is negative.
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The majority of internal parasites are diagnosed by microscopic examination of the feces for eggs that are released by the adult female in your pet's intestine. The number of eggs released in a given fecal sample can be variable, sometimes there aren't any even though your pet has an adult female parasite in its intestines.
This means that a negative fecal report does not guarantee that your pet is free from internal parasites. In many cases we need to run numerous samples to feel comfortable that your pet is free of internal parasites. In some cases our doctor's will treat for a specific parasite, even on a negative fecal sample, when they feel there is a likelihood of infestation, because some internal parasites eggs are notoriously hard to detect.
In some parasites a diagnosis is made by observation of the mature parasite in your pet's feces or during an autopsy in your pet's intestines. This is especially true for Tapeworms. Tapeworm eggs are difficult to detect during microscopic fecal analysis, so observation of the actual worm is how they are routinely diagnosed.
The two primary methods of fecal analysis are direct observation and fecal flotation. In direct observation a smear is made of some fecal material on a microscope slide and the slide is analyzed by one of our nurses for parasite eggs. It is used to detect eggs that don't show up well during the fecal flotation.
Fecal flotation is the most accurate way to detect most internal parasites. A sample of fresh feces is put into a special solution that causes any eggs that might be present to float to the top and adhere to a cover slip. The cover slip is put on a microscope slide for analysis. This concentration of eggs substantially increases the chance of finding any eggs that might be present. Some eggs, notably Tapeworm eggs, dissolve during this process and might be undetected. This is the reason you can see Tapeworms in your pets stool yet the fecal analysis came back negative.
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We have sanitary containers for you to use to obtain a fecal sample from your pet. Once the sample is obtained it should be kept cool until we analyze it. Analysis should be within 12 hours to increase accuracy.
The flotation solution has been added to the fecal container and a cover slip has been placed on the top to collect any eggs that float to the surface after a 5 minute wait.
The cover slip is put on a microscope slide and carefully scanned for the eggs of any parasite.
Internal parasites have very sophisticated life cycles that can make treatment difficult. Some of these life cycles involve mandatory maturation processes in other animals, including insects. Specific treatment modalities are set up to address these life cycles and will be discussed for each individual parasite in the following sections. It is important to follow these treatment regimens precisely.
Some parasites can only be controlled, not eliminated. In these cases it is important to check your pet's feces routinely and to use medication on a long term basis.
There are new treatments for internal parasites that are very broad spectrum. They kill a wide variety of parasites, and are the medications we use as a routine wormer.
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What are Hookworms?
If you look at the picture you will notice that the "business end" of the Hookworm is shaped like a tiny goblet with three sets of teeth. The goblet-shaped mouth is very hard and resists collapse as the worm sucks. The Hookworm grasps onto the inner surface of the small intestine with the teeth and then pierces a blood vessel. An anti-coagulant saliva-like substance is released which prevents the blood from clotting. Each hookworm can suck 0.1cc of blood per day. If they release the wound continues to bleed.
How do our pets get Hookworms?
Kittens or puppies may be born with Hookworms! Hookworm larva are tiny enough to migrate through the placental blood supply to the fetal lungs. Soon after birth, the juvenile Hookworms are coughed up and swallowed. They then mature in the small intestine; attach to the intestinal wall and begin sucking blood and laying eggs.
A second source of infection is through the mother's milk - Hookworm larva can gain entry into the mammary glands and be passed to the puppies or kittens as they nurse. The larva then mature in the intestine to form blood sucking adults.
The third possibility is if the pet should swallow a Hookworm larva found in the environment (like on a blade of grass, a toy, water or food dish). The Hookworm larva mature to adults in the intestine as above. Soon after feeding on blood the Hookworm adults begin laying eggs which pass with the feces. Under favorable conditions (moisture and warmth) the eggs hatch within 12 to 18 hours and a tiny juvenile Hookworm emerges. This larva is encased within a sheath that offers protection against dessication and ensures long life in the environment. The larva reside in moist areas of the soil and overlying vegetation.
The most important mode of transmission is unique! I mentioned above how the eggs pass with the feces and hatch within 12 - 18 hours on moist ground. The newly hatched larva then become free-living organisms which thrive in moist soil or on damp grass awns. Another interesting thing is that the larva can live for many weeks without food.
These free-living larva are able to penetrate the intact skin of dogs or cats passing by or as a pet lies on the ground the heat excites the larva and they go right through the thin skin of the ventral abdomen. Picture this! You take your dog on a walk in a park where Hookworm infested dogs have deficated. As your pet passes through the wet grass an infective juvenile Hookworm brushes onto the paw. The larva easily penetrate the skin and follow a blood vessel to the lungs. From there the worm is coughed up and swallowed to mature in the intestine; begin sucking blood and laying eggs.
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What are the signs of Hookworm infestation?
Signs may include any or all of the following: Inapparent infestations; nonspecific diarrhea; dark black (tarry) diarrhea; bloody diarrhea; vomiting; poor or no appetite, pale mucous membranes in the mouth and generalized pallor; weakness, emaciation and poor growth. Anemia can be so severe as to cause death.
What is the treatment?
It is easy to get rid of Hookworms. Just give any effective oral wormer. My favorite is any brand with pyrantel pamoate as the active ingredient. This is generally well tolerated by the pet, safe and effective. If the animal is severely anemic, blood transfusions and supportive care may be required. It is best to worm breeding female dogs and cats before breeding and again 3, 6 and 9 weeks after whelping. Juveniles migrating through the body will not be killed by conventional wormers.
This is why we like to worm puppies and kittens twice three weeks apart and then check a fecal specimen three weeks later. This allows all migrating juveniles to reach the intestine where they are easily killed. Since Hookworm eggs and larva build up in damp soil, often times the dogs tied out on dirt or in soil runs need to be moved to a non-infested area to prevent reinfection. If this is impossible and the pet keeps becoming reinfected, I suggest keeping the dog on Filaribits Plus (a daily heartworm preventative with a low level wormer included which kills Hookworms, Roundworms and Whipworms) for a year or more while the Hookworm larva and eggs die off. Concrete surfaced runs or runs with deep pebble coverings allow the surface to dry allowing sunlight to kill the larvae. Fecal Examinations: Young dogs and cats should have a fecal floatation done twice a year to detect Hookworm eggs.
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