Flea Infestation in a Cat
History. A cat is presented to you because the owner notices that the cat seems extremely weak and recently has been staggering when it walks around the house. The cat’s appetite is good, and besides the weakness, the owner thinks the cat is normal.
Clinical Examination. Inspection of the animal, which is resting quietly on the examination table, shows that it is in reasonably good condition. The respiratory rate does not appear to be elevated, and from a distance the cat shows no obvious signs of disease. When you place your hands on the cat’s back, you immediately notice a gritty material in the fur. Further examination of the skin shows accumulations of this red- brown material deep within the coat, and you notice many fleas scurrying around when the coat is parted. When you moisten some of the gritty material, it produces a red liquid. The cat’s mucous membranes are almost white, and the examination of the mucous membranes produces sufficient struggling that the cat begins to breathe rapidly. The cat’s pulse rate is extremely elevated, but the lung sounds are normal. On physical examination, all the body systems appear to be normal. You take a blood sample; the packed cell volume (hematocrit) is 10% (normal, 30%-45%).
Comment. This cat has a severe infestation of fleas. The gritty material in the fur is flea feces, which contains blood products that become red when wet. The infestation is further confirmed by the observation of many fleas in the coat. By their blood-sucking method of feeding, fleas can produce anemia when they are present in large numbers, as with this cat. If the flea infestation develops gradually, the anemia is slow in onset, and the host animal may show few clinical signs until the infestation and anemia become severe. The anemia is confirmed in this case by the paleness of the mucous membranes and by the low hematocrit.
The rapid heart rate of the cat is a response to the anemia. To deliver sufficient oxygen to the tissues, the cardiac output needed to be increased by increasing the heart rate. When the cat is stressed by your examination, it shows signs of respiratory distress because there is inadequate oxygen delivery to the tissues; this causes production of lactic acid as a result of anaerobic metabolism. The resultant decrease in pH stimulates the chemoreceptors, causing the signs of respiratory distress.Treatment. Your treatment approach to this cat is twofold. First, you administer blood to increase the cat’s hematocrit and provide it with sufficient oxygen-carrying capacity until it can generate new erythrocytes. Second, you treat the flea infestation and instruct the owner on how to remove the fleas from the house.
Several weeks later the owner returns with the cat and notes that she has had no further problems. Occasionally she notes a flea on the cat’s coat and treats the cat immediately with flea medication. She is also diligent about regular vacuuming to remove fleas from the house.