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Lactase persistence or lactose tolerance is the continued activity of the lactase enzyme in adulthood, allowing the digestion of lactose in milk.In most mammals, the activity of the enzyme is dramatically reduced after weaning. [1]
Unlike mammals, the red blood cells of fish have DNA, and can become infected with viruses. The fish develop pale gills, and may swim close to the water surface, gulping for air. However, the disease can also develop without the fish showing any external signs of illness, the fish maintain a normal appetite, and then they suddenly die.
The majority of humans actually follow this protocol as well, and down-regulate lactase production around 3-5 years of age. Interestingly, though, the majority of caucasians, mainly those from northern european background, continue to have elevated lactase activity all the way into adulthood, and so they exhibit “lactase persistence”.
The infected fish also becomes lethargic, swims near the surface, and its appetite decreases. [10] Additionally the infected fish may hold its gill covers open and scratch its gills on rocks. [14] In severe infections, Dactylogyrus species can cause hemorrhaging and metaplasia of the gills which can lead to secondary bacterial infections and ...
P. multocida is the cause of a range of diseases in mammals and birds, including fowl cholera in poultry, atrophic rhinitis in pigs, and bovine hemorrhagic septicemia in cattle and buffalo. It can also cause a zoonotic infection in humans, which typically is a result of bites or scratches from domestic pets.
This category is dedicated to the various Fish diseases. For an overview of this subject go to Fish diseases. Subcategories.
Henneguya zschokkei is found in fish as an ovoid spore with two anterior polar capsules and two long caudal appendages. [6] Individuals are very small (about 10 micrometers in diameter), [7] but are found aggregated into cysts 3–6 mm in diameter at any place in the animal's musculature. [8]
Lactase persistence is a rare ability among mammals. [74] Because it involves a single gene, it is a simple example of convergent evolution in humans. Other examples of convergent evolution, such as the light skin of Europeans and East Asians or the various means of resistance to malaria, are much more complicated. [16]