Rickettsiosis
Rickettsiosis is a bacterial disease that requires the cells of an organism to survive, since they cannot survive in the environment.
Rickettsia rickettsi causes Rocky Mountain sickness and primarily affects domestic dogs. The bacteria attacks the cells that line blood vessels, destroying them and causing inflammation and bleeding in affected dogs.
The disease is important for public health because it can be transmitted to humans after being bitten by the brown dog tick.
Clinical signs
In affected individuals, the disease manifests with fever up to 40.5°C, anorexia, swollen lymph nodes, arthritis, difficulty breathing, abdominal pain, vomiting, diarrhea, cough, and muscle pain.
When the disease progresses severely, it can affect the nervous system, causing mental disturbances, behavioral changes in dogs, tremors, and difficulty walking. Red eyes, vision problems, nosebleeds, and blood in urine and feces may also be observed.
Rocky Mountain spotted fever has a characteristic sign, the appearance of small reddish spots on the skin (known as macular rashes).
In general terms, the signs are due to the destruction of the blood vessel walls and the inflammation caused by this destruction (vasculitis).
Transmission
The disease is transmitted directly after a tick bite, or by handling the tissues and blood of an infected animal.
In Mexico, the disease is transmitted by the brown dog tick ( R. sanguineus ). It can also be transmitted by the American dog tick ( Dermacentor variabilis ) and the Rocky Mountain woodland tick ( Dermacentor andersoni ), both of which are found in the United States.
Some small mammals, such as rats and mice, serve as reservoirs for the disease. These animals are also parasitized by ticks and can spread the disease to dogs and humans.
Direct transmission from dogs to humans has not been reported, so dog bites do not transmit the disease.
Disease management
The disease should be suspected if any of these clinical signs are present, along with a history of tick bites, in both dogs and humans. Early detection of the disease is vital to prevent the condition from worsening; immediate medical attention is recommended for specific treatment.
To avoid the risk of contracting the disease, it is recommended to control the tick population on dogs in the home, as people sometimes do not realize they have been bitten by a tick. Dogs in the home should be examined for ticks and treated accordingly with the help of a veterinarian.
Because mice serve as a reservoir, ticks carrying the bacteria can be found far from human populations. When traveling to an area where ticks are present, it is necessary to wear protective clothing and insect repellent, in addition to conducting a thorough tick inspection.