Final answer:
The most likely cause of the symptoms in the husky, including petechiae, bleeding gums, and lethargy, is likely to be leukemia, which can result in a low platelet count leading to bleeding disorders.
Step-by-step explanation:
The clinical signs described for the husky - petechiae on his abdomen, bleeding gums, and lethargy - are indicative of bleeding disorders which may have various etiologies. One possible cause could be immune-mediated thrombocytopenia, which is not explicitly listed in the options provided. Out of the given choices, the most fitting would be leukemia, which can cause thrombocytopenia (a low platelet count), leading to the observed symptoms of petechiae and bleeding gums. While hepatitis, parvovirus, and rabies are also serious conditions affecting canines, none of these typically presents with the described combination of predominantly hemorrhagic (bleeding) symptoms.
Leukemia affects the bone marrow and leads to production of abnormal white blood cells, which can crowd out the normal blood cells, including platelets, responsible for clotting. When platelets are low, spontaneous bleeding such as petechiae and bleeding gums can occur, along with general symptoms of malaise such as lethargy.