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Ancylostoma caninum is the most common dog hookworm. Infection occurs either by ingestion of the microscopic, infective stage larvae, or by larval penetration of the skin. The larvae eventually get to the intestine where they mature into adults. The worm is a blood sucker. Adult dogs may or may not show clinical signs but in young animals, severe anemia may occur. The gums will be pale, the puppy weak and emaciated and there may be diarrhea.
Dirofilaria immitis, the canine heart worm is found as an adult coiled in the heart ventricles, pulmonary artery and the vena cava. The adults mate and hatch microfilaria which circulate throughout the dog's vascular system. When a mosquito feeds on an infected dog, it swallows these microfilaria along with the blood. In a few days, the microfilaria develop into larvae and migrate to the head and mouth parts of the mosquito. When the mosquito then bites another dog, these developed larvae are ejected with mosquito saliva into the new dog and the cycle starts again. Potential harmful effects are related to mechanical interference with blood flow and heart function (there may be a few, or hundreds of adults lodged in the heart). Clinical signs include heart failure, ascites, and pulmonary congestions and cough. Diagnosis is made by examining blood for the presence of the microfilaria or the antigen made in response to the adult heartworm. Treatment to rid the dog of adult heart worms has many life-threatening side affects and veterinarians concentrate on prevention. The microfilaria can be easily killed by monthly or daily treatment.
Tapeworms: Adult tapeworms generally have minimal effects on the dog. However, the risk to humans from certain species of tapeworms makes elimination of these parasites a high priority (not to mention the aversion people have to finding tapeworm segments in the feces and around the anus of affected dogs).
Giardia, Coccidiosis: Protozoan organisms are frequently implicated in outbreaks of diarrhea. It may be that protozoa are always present in low numbers, but then multiply rapidly when dogs are under stress, such as when weaned or transported.
Fleas: Ctenocephalides canis is the common dog flea but if the preferred host (the dog) is not available, the flea will jump onto any other species (the human). The life cycle is mostly off host in the bedding or in the grass. Repeated treatments are required to eliminate the newly hatched fleas and eggs can remain viable and dormant for some time.
Sarcoptic Mites: The female mite works her way deep into the skin forming tunnels where they deposit eggs. Close proximity to nerve endings cause intense puritis (itching). The skin thickens and dense crusts form. The dog can cause further damage from scratching the affected skin. Often infected dogs will have "mange", substantial hair loss and their skin will be wrinkled, thickened and covered with sores and scabs. Treatment requires bathing dipping with a miticide and secondary bacterial infections require systemic antibiotics.
Otodectes cynotis, the ear mite, is extremely common; between 30-100% of the dogs examined will have these mites. The mite is transmitted from one animal to another by direct contact and by contaminated bedding, caging and other equipment. The mite is usually found deep in the ear where they cause cerumen to build up. Secondary bacterial infections are common so the ear canal often shows a dark waxy exudate. Because the mite will be present in the environment, treatment must be daily for at least 10-14 days.
Demodex canis mite commonly lives in the follicles of the skin. The mite is probably transmitted from mother to young during nursing but this has not been proven. The mite is present on almost ALL dogs, and usually there are no clinical signs! Probably due to some unknown immune problem, certain dogs show explosive disease called "red mange". The entire skin may be affected and due to the high blood flow to the skin, there will be a reddish cast. Secondary bacterial infections may cause the skin to be pustular. Treatment of these types of affected dogs may be difficult (there is probably an underlying immune problem).
Ticks: All ticks pass through four life stages: egg, larva (seed tick), nymph and adult and all but the eggs are parasitic and feed on blood. Ticks are not very host specific. Control is by examining newly acquired animals and treating if infested. Ticks are not only annoying, ugly and debilitating, but they surpass all other anthropoids in the variety of disease agents they transmit: Rocky Mountain Spotted Fever, Lyme Disease, Typhus, and Erlichia.
Coccidiodomycosis (Valley Fever): A fungal infection which is endemic in the semi-arid regions of the southwest. Infections occurs by inhalation of airborne spores of the fungus, Coccidioides immitis. These fungal spores become airborne when soil is disturbed by digging, or construction projects. Rodent burrows are another source of the infective organism and the propensity of dogs to sniff holes may be why dogs are more often affected. Symptoms depend on what happens after the spores enter the deep tissue of the lung: 1) the spores are usually walled off by the body's defense mechanisms and only a mild respiratory problem with coughing is observed. 2) If the organism is not walled off in the lung, but disseminates throughout the body, almost all organs can be affected and without treatment, these animals will die. Symptoms vary according to which organs are most severely affected, but often the long bones are heavily invaded and the animal will become lame or sore on palpation of the limb. Treatment is ketaconazole given for a minimum of six months.
Rabies: A natural viral disease of dogs, cats, bats and wild carnivores, but all warm blooded animals are susceptible. Once the virus infects the CNS the outcome is invariably fatal. The virus is transmitted by infected saliva, usually by a bite wound, but viral laden saliva may enter preexisting wounds or abrasions. Infection takes place by deposition of infected saliva in or near a nerve. The virus travels up the nerve to the spinal cord and finally reaches the brain. After a variable incubation period, rabid animals will exhibit signs related to CNS disfunction: any alteration in behavior is reason to suspect rabies. There is a great diversity in clinical signs: some animals simply have a change in the sound of their bark, others become very quiet and timid, others may act as though they are choking, or their lower jaw paralyzed, some infected dogs will roam long distances and snap at anything that moves (these classic "mad dogs" often chew and swallow objects such as sticks and stones). For treatment to be effective, the exposed animal or person must be treated during the incubation period, before the virus reaches the CNS. The earlier the treatment, the more hopeful the outcome. If there is human exposure to an unvaccinated dog suspected of rabies, the dog is euthanatized and tissues submitted for fluorescent antibody staining. Depending on the State and the vaccination history, a vaccinated dog suspected of rabies that bites a human will be confined for 10 days to 4 months. If any suspicious signs occur during the quarantine period, the dog is euthanatized and tissues collected for testing. Preventative vaccines for dogs are available and required by all states. Preexposure vaccines are also available for animal shelter employees, veterinarians and laboratory animal caretakers.
Infectious canine distemper: The degree of illness correlates with the level of antibody which develops in response to the virus. About half of dogs exposed to the virus will develop titers less than 1:100 and the infection becomes widespread. About two weeks after infection, the dog shows severe depression, anorexia, dehydration and weight loss. Usually there is a mucopurulent (pus) ocular and nasal discharge, and often there is vomiting and diarrhea. Even with medical aid, these dogs usually die within a matter of weeks. Most of the half of the dogs which develop antibody titers greater than 1:100 will never manifest clinical signs. But, about 1/5 of these "high titer" dogs will show problems long after exposure anywhere from 15 days to many months later. For unknown reasons, in these dogs, the virus is able to "hide" from the circulating antibodies in the epithelial tissue of foot pads and brain. In these dogs, the pads of the bottom of the feet become thickened (Hard pad disease) and the dogs show a variety of CNS signs: 1) Myoclonic twitching of muscle groups 2) Posterior paresis or paralysis, 3) Generalized seizures, 4) Psychic or behavioral changes, 5) "Old Dog" Encephalitis with progressive mental and motor deterioration until the dog finally dies. Diagnosis is confirmed by fluorescent antibody staining of viral antigen in the diarrhea, footpads, or CNS tissues.
Canine Respiratory Disease (sometimes called Kennel Cough). Numerous viral and bacterial agents may be involved, including: Canine Distemper Virus (CDV), Canine Adenovirus I (CAV I), Canine Adenovirus II (CAV II), Canine Parainfluenza Virus, Mycoplasma sp. and Bordetella bronchiseptica. Once a virus damages the epithelium of the upper respiratory tract, the defense system is compromised and ineffective for removing bacterial pathogens. The resulting bacterial pneumonia then potentiates the viral infection. Two main types of disease are seen: 1) Mild, uncomplicated tracheobronchitis in dogs with good vaccination history for CDV and CAV I. Typical dry, harsh cough which after a few coughs may sound like dry retching. (Many times it sounds as though the dog has something stuck in it's throat). These dogs are usually afebrile, bright and alert. 2) Complicated type of tracheobronchitis with dry to moist cough, fever, depression, mucoid rhinitis, dyspnea. Treatment consists of antibiotics, anti-cough medications and supportive care. Prevention is through vaccination for the known viral agents: CDV, CAV I and CAV II, Canine Parainfluenza Virus.
Canine Parvo Virus (CPV): In August 1978 the Midwestern states reported a series of diarrheal outbreaks, later proved to be due to this parvo virus (which is a different virus than the parvo virus which infects rodents). A survey of stored, frozen sera from 1976 to 1978 failed to detect parvo virus antibody, which suggests that this virus was new. The virus is highly infective and survives in fecal matter for months. Dogs of all ages are susceptible; signs vary greatly. The feces change from light grey to mucoid to bloody to frank hemorrhage. The diarrhea may be projectile and explosive which leads to dehydration and death from shock in 24-48 hours. When infected in utero, CPV may cause myocarditis and acute congestive heart failure in 4-12 week old puppies. Treatment is symptomatic. A vaccine is available, but because the virus rapidly mutates, it fails to protect dogs all of the time.
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