There are a ton of reasons why dogs begin showing aggression towards other dogs, and the best way to fix that sort of behavior is fixing it RIGHT AWAY.

You want to remain cool, calm and collect, at all times and evaluate why it is, exactly, that your dog is doing this.

I wrote more on this in the blog post linked in the source, below.

I really hope that it helps you out and good luck!

And for purebred dogs find the national breed club website and look for a breeder directory.

Dynamics Of The Disease

Parvovirus is an extremely tough and resistant bug. The virus lives for long periods of time on floors, food containers and other household objects. Rugs are particularly difficult to sanitize. It is thought that household vermin such as cockroaches move the virus from place to place. The virus is both resistant to phenolic disinfectants and to heat. It can be inactivated, however, with ordinary household bleach used at a concentration of one part bleach to twenty parts water. Exposure to sunshine also kills the virus. For the bleach solution to work, any caked organic material must first be removed by washing.

Although it takes one or two weeks for the dog to develop signs of disease, the virus is shed in the feces from the third day of exposure onward. This means that dogs that appear healthy can already be shedding the virus and contaminating the home.

The Symptoms of Parvo

Parvovirus disease is remarkable in that symptoms can vary from none at all to a fatal disease. Four factors govern the severity of the disease: age at exposure, the size of the virus dose, the presence of maternal antibody, and the breed of dog involved.
Dogs receive transient maternal antibody from their mothers through their first milk or colostrum. This antibody gives the puppy resistance to the disease. Puppies that are housed in a parvo-filled environment rarely break with the disease until they reach 14-20 weeks of age. At that time their mother’s immunity no longer protects them and they may die of the disease.
Dogs over six month of age develop natural resistance to the effects of parvovirus. Many of these dogs show only transient diarrhea. By the time the dog reaches one or two years of age the disease can be so mild that it passes unnoticed by the owners.
For unknown reasons, Doberman Pinschers, Rottweilers and Pit Bull Terriers become more ill with this disease than other breeds.

The most common form of parvovirus infection is a sudden (acute) inflammation of the small intestine or enteritis. This is characterized by depression, vomiting, diarrhea and profound dehydration. Bloody stools and a drop in white blood cell numbers are common. Some puppies die as soon as diarrhea occurs but many linger on for 4-6 days. Those that survive eight days usually recover. The lack of white blood cells and ulceration of the lining of the small intestine lead to secondary bacterial infections. There are many other virus and bacteria that can cause bloody diarrhea in dogs. This leads to misdiagnosis where not all cases of “Parvo” in puppies and adults are actually due to this virus.

Diagnosis

Although symptoms can be very suggestive of Parvo, true diagnosis requires an antibody test that detects the actual parvovirus in stool samples. The test is an ELISA test or enzyme-linked immunosorbent assay. You can read about the Idexx brand of that test here. Early in the disease, this test can be negative. Virus isolation is possible but the procedure is quite expensive and rarely done. In practice, the presence of an acute hemorrhagic diarrhea is usually all that is required for a tentative diagnosis of parvovirus.

Treatment

Treatment of parvovirus is directed at correcting the life-threatening dehydration that accompanies the diarrhea with intravenous fluids (lactated ringers solution with bicarbonate). Ten to forty milliliters per pound is given initially and then a slow intravenous drip may stabilize these dogs. Once the initial dehydration is corrected, maintenance fluids can also be given subcutaneously. We also give medicines that relax intestinal spasms such as metoclopramide (Reglan, 0.1-0.25mg/lb three or four times a day) and trimethobenzamide (Tigan, 1.5mg/lb three times a day). Besides this, the dogs are placed on antibiotics to prevent secondary bacterial infection through the damaged small intestine (cephalothin, Keflin @ 5-15mg/pound given four times a day intramuscularly or intravenously). Early in the disease dogs may run a short period of fever. But puppies’ temperatures often drop to subnormal a few days later. These dogs need additional sources of heat. It helps to sit with the dog, pet it and encourage its will to live. Many of the younger dogs have hookworm infestations that make the parvovirus disease more severe. As soon as these dogs can hold down liquids, I worm them with pyrantel pamoate (Strongid, Nemex, 2.5mg/pound).
Some veterinarians give the dogs small doses of butorphanol tar

Dogs are clearly wild animals, let them be wild, they are unsafe.

Oh and it isn’t just ALWAYS because the owner has treated them bad.
I was biten by a random dog for no reason.
I was at a park, dog was running lose and attacked me.

PEOPLE ARE MORONIC SCUM IN GENERAL , AND DOGS ARE DANGEROUS
A LOT OF LITTLE BOYS WITH SMALL PENISES LIKE TO HAVE A BIG DOG BECAUSE THEY CANT FIGHT AND THEY FEEL SCARED,
PEOPLE SHOULDNT BE ALLOWED DOGS WITHOUT A LICENSE, LIKE A GUN . OR ANYTHING ELSE WHICH CAN KILL

Hotdogs for sale!
Where, where?
Hotdogs for sale!

But where, but where, but where?
Over there by the beef burgers.

No just peanuts and bananas.