Conjunctival suffusion is an eye finding occurring early in Weil’s disease, which is caused by "Leptospira interrogans". Conjunctival suffusion is characterized by redness of the conjunctiva that resembles conjunctivitis, but it does not involve inflammatory exudates. Swelling of the conjunctiva (chemosis) is seen along the corners of the eye (palpebral fissures).

About 30 percent of patients with Weil's disease develop conjunctival suffusion. When it does occur, it develops towards the end of the early phase of the illness. Even in severe cases, the suffusion occurs in the first phase of the illness.

Conjunctival suffusion may also occur in patients with a Hantavirus infection. In a 1994 study of 17 patients with Hantavirus infections, 3 had conjunctival suffusion.

Incubation (time of exposure to first symptoms) in animals is anywhere from 2 to 20 days. In dogs, leptospirosis most often damages the liver and kidney. In addition, recent reports describe a pulmonary form of canine leptospirosis associated with severe hemorrhage in the lungs—similar to human pulmonary hemorrhagic syndrome. Vasculitis may occur, causing edema and potentially disseminated intravascular coagulation (DIC). Myocarditis, pericarditis, meningitis, and uveitis are also possible sequelae.

At least five important serovars exist in the United States and Canada, all of which cause disease in dogs:>

- Icterohaemorrhagiae

- Canicola

- Pomona

- Grippotyphosa

- Bratislava

In dogs when leptospirosis is caused by "L. interrogans" it may be referred to as "canicola fever". Leptospirosis should be strongly suspected and included as part of a differential diagnosis if the sclerae of a dog's eyes appear jaundiced (even slightly yellow). The absence of jaundice does not eliminate the possibility of leptospirosis, and its presence could indicate hepatitis or other liver pathology rather than leptospirosis. Vomiting, fever, failure to eat, reduced urine output, unusually dark or brown urine, and lethargy are also indications of the disease.

In dogs, penicillin is most commonly used to end the leptospiremic phase (infection of the blood), and doxycycline is used to eliminate the carrier state.

Effective antibiotics include penicillin G, ampicillin, amoxicillin and doxycycline. In more severe cases cefotaxime or ceftriaxone should be preferred.

Glucose and salt solution infusions may be administered; dialysis is used in serious cases. Elevations of serum potassium are common and if the potassium level gets too high special measures must be taken. Serum phosphorus levels may likewise increase to unacceptable levels due to kidney failure.

Treatment for hyperphosphatemia consists of treating the underlying disease, dialysis where appropriate, or oral administration of calcium carbonate, but not without first checking the serum calcium levels (these two levels are related). Administration of corticosteroids in gradually reduced doses (e.g., prednisolone) for 7–10 days is recommended by some specialists in cases of severe hemorrhagic effects. Organ-specific care and treatment are essential in cases of kidney, liver, or heart involvement.

Preventing Omsk Hemorrhagic Fever consists primarily in avoiding being exposed to tick. Persons engaged in camping, farming, forestry, hunting (especially the Siberian muskrat) are at greater risk and should wear protective clothing or use insect repellent for protection. The same is generally recommended for persons at sheltered locations.

Omsk Hemorrhagic Fever could be diagnosed by isolating virus from blood, or by serologic testing using immunosorbent serological assay. OHF rating of fatality is 0.5–3%. There is no specific treatment for OHF so far but one way to help get rid of OHF is by supportive therapy. Supportive therapy helps maintain hydration and helps to provide precautions for patients with bleeding disorders.