animal has trouble breathing, starts coughing frothy fluid from nostril and mouth, and shows signs of pulmonary edema within four days. Serious lung congestion causes respiratory failure and results in death in under 24 hours. This form of the disease has the second highest mortality rate. Other symptoms include swelling of the lymph nodes under the jaw, and levelled swelling above the eyes. This form does not have as much swelling on the brain as the Cardiac form, the swelling is mostly around the organs Cardiac form This subacute form of the disease has an incubation period longer than that of the pulmonary form. Signs of disease start at day 7–12 after infection. High fever is a common symptom. The disease also manifests as conjunctivitis, with abdominal pain and progressive dyspnea. Additionally, edema is presented under the skin of the head and neck, most notably in swelling of the supraorbital fossae, palpebral conjunctiva, and intermandibular space. Mortality rate is between 50 and 70%, and survivors recover in 7 days. This form does not have such a high mortality rate, but the lymph nodes and above the eyes are not as swelled. The swelling above the eyes are a sign that the brain is swollen, and if it is too much the eyes will pop out. If treated correctly the animals has a higher chance of surviving. Mild or horse sickness fever form Mild to subclinical disease is seen in zebras and African donkeys. Infected animals may have a low-grade fever and congested mucous membrane. The survival rate is 100%. Mixed form Diagnosis is made at necropsy. Affected horses show signs of both the pulmonary and cardiac forms of AHS. This form probably has the highest mortality rate of all the forms. Not many survive this. Diagnosis Presumptive diagnosis is made by characteristic clinical signs, post mortem lesions, and presence of competent vectors. Laboratory confirmation is by viral isolation, with such techniques as quantitative PCR for detecting viral RNA, antigen capture (ELISA), and immunofluorescence of infected tissues. Serological tests are only useful for detecting recovered animals, as sick animals die before they are able to mount effective immune responses. Treatment and prevention No treatment for AHS is known. Control of an outbreak in an endemic region involves quarantine, vector control, and vaccination. To prevent this disease, the affected horses are usually slaughtered, and the uninfected horses are vaccinated against the virus.