Most parasites in puppies (such as intestinal worms, or fleas) are unlikely to do any real harm to your puppy in the short-term.
But it's essential to treat them quickly, or they will turn into a serious threat to his health.
Other parasites such as heartworms, ticks, giardia protozoa and others are dangerous from day one.
Some of these nasties live inside your pup, maybe in his colon, lungs or even his heart.
Others take up residence on the outside, making themselves at home in his fur or on his skin.
Symptoms ranging from diarrhea and vomiting, to skin irritation, intense itching, coughing, anemia... even pneumonia or death.
They may be tiny, but you need to take them seriously!
The ones you're most likely to see in young puppies are worms, single-cell protozoa, fleas and skin mites.
Scroll down to take a closer look at all of these:
Although they're common, worms in puppies can lead to serious health issues if you don't treat them promptly.
There are several different types of worms that can set up shop in your puppy's digestive system, the most common ones being Roundworms, Tapeworms, Hookworms and Whipworms.
Loose stools, or even diarrhea, and/or vomiting are common symptoms of a worm infestation, but there are other more subtle (or unexpected) signs that your puppy might be harboring some tiny, intestinal fugitives!
These include pale gums, swollen belly, dry coat and more.
Click here to learn more about diagnosing and treating puppy worms.
Tiny protozoa may always be present in your puppy's digestive tract, but his natural immunity keeps them at bay.
But if he gets sick, or very stressed (either physically or emotionally), his immune function nose-dives and these nasty little creatures start to flourish and over-run his body.
The most common symptoms of this type of illness are repeated diarrhea and maybe vomiting. The diarrhea is often watery and very smelly. It may contain some mucus or even streaks of blood.
Weakness or lethargy and/or a fever (anything over 102F) are also common.
Heartworms are another, very dangerous type of internal parasite.
Rather than settle in the digestive tract, these worms migrate to your pup's heart where they grow and multiply until they cause heart failure and death.
You won't see any symptoms of heartworm in a puppy under 6 months old, because that's how long it takes for the worms to cause serious problems.
But by the time a pup or dog has had heartworms in his body for that period of time, he's already in BIG trouble!
So, it's vitally important to get your pup started on a monthly heartworm preventative as soon as he's 8 weeks old.
Everything you need to know about Heartworm Prevention
Both fleas and ticks in dogs can cause all sorts of problems.
Let's start with fleas...... because they're hardy, breed quickly and can make your puppy absolutely miserable.
Fleas take up residence in your pup's fur and survive by biting him and drinking his blood. Sounds yukky I know!
Obviously this isn't good for your pup and although he's unlikely to be losing a lot of blood (unless he's very tiny or young and has a severe infestation), he IS going to be very itchy and uncomfortable.
Many puppies and dogs are allergic to flea saliva and when they're bitten they suffer from an allergic reaction that causes intense itching and irritation.
This is followed by some intense scratching which can make matters worse, making skin raw, swollen or scabby. Localized infection isn't uncommon either.
This isn't the only problem fleas cause. They can also be a potential source of disease (such as Rocky Mountain Spotted Fever) and transmit tapeworms.
Ticks are equally nasty and suck your puppy's blood on a much bigger scale. They also spread infections such as Lyme Disease and Ehrlichiosis. A severe tick infestation can cause your puppy to get very sick indeed due to loss of blood.
Click here to find the best medications to prevent & eliminate fleas and ticks
Another type of external puppy parasite is the Mite. These tiny guys are part of the spider family (so are ticks) and there are several different types of mite.
They usually live on your pup's skin or on the hair follicles (but unlike fleas these critters are generally too small to see with the naked eye), but there is a species of mite that prefers to take up residence in your puppy's delicate ears.
Mites can cause skin irritation, rashes, red or scaly skin, patchy hair loss or baldness and even what looks like really bad dandruff.
One of the most common types of mite is the Demodex Canis. It causes a condition called Demodectic Mange.
The Sarcoptes mite causes Sarcoptic Mange (aka 'Scabies' which can be transmitted to humans).
Find out about diagnosing and treating Mange.