Heartworms are spaghetti-like worms that infest dogs. Like most parasites, the heartworm goes through several life stages before emerging as an adult and needs at least two hosts to complete the cycle. The mosquito serves as the host for heartworms in the larval stage, or baby heartworms, called microfilariae. The mosquito ingests the microfilariae when it bites an infected dog and deposits them in an uninfected dog when seeking another blood meal. Adult heartworms can reach 30.5 centimetres in length. The worms grow and multiply, infesting the chambers on the right side of the heart and the arteries in the lungs. They can also lodge in the veins of the liver. The first sign of heartworm infestation may not appear for a year after infection, and even then the soft cough that increases with exercise may be dismissed as unimportant by the dog's owner. But the cough worsens and the dog may actually faint from exertion. It tires easily, is weak and listless, loses weight and may cough up blood. Treatment is possible if the disease has not progressed too far. Heartworms can be detected by a blood test. However, if discovered too late, the dog cannot be cured. Preventive medicine is available from veterinarians and can be given daily or monthly. Heartworms have been found in cats, although they are not a 'normal' host, meaning the heartworm does not grow and reproduce in them as it does in 'normal' hosts - dogs. Its growth is stunted and it will die after a few years. Can humans contract heartworms? At this point, heartworms cannot hide from our immune system. There's a story about fish that can walk on land. Is this true? Several varieties of fish around the world can 'walk' by digging their pectoral fins into the turf in the manner of soldiers crawling over an obstacle course. One of the most prevalent is the 'walking catfish' (Clarias batrachus ), which was imported into Florida from Thailand during the 1960s as part of the tropical fish trade. Some of the fish literally walked away from their holding ponds and kept going. Over the years, they have multiplied into the millions and are now fairly common in the lower half of Florida. What are hot springs and do they have medicinal value? In hot springs, groundwater, at a higher temperature than that of the human body, emerges from the land surface, either as a steady trickle into pools or in a more spectacular way as geysers, shooting into the air. The hot water may be heavily charged with sulphur and consequently have a strong smell. Such pungent hot-water springs were used as health spas, particularly in Victorian times in Britain. A famous devotee of hot springs for medicinal purposes was Charles Darwin.