PROHIBITION OF PORK
Pork is the meat of animal pig.
“It is not for a believer, man or woman, when Allah and His Messenger have decreed a matter that they should have any option in their decision. And whoever disobeys Allah and His Messenger, he has indeed strayed into a plain error” Qur’an.Surah Ahzab 33:36
“The only saying of the faithful believers, when they are called to Allah (His Words, the Qur’an) and His Messenger, to judge between them, is that they say: ‘We hear and we obey.’ And such are the successful (who will live forever in Paradise)” Qur’an.Surah Nur 24:51
Pork is forbidden in Islam according to Qur’an, where Allah says (interpretation of the meaning): “He has forbidden you only the Maytah (dead animals), and blood, and the flesh of swine…” Qur’an.Surah Baqarah 2:173, Surah Maidah 5:3 and Surah Anam 6:145.
It is not permissible for a Muslim to consume it under any circumstances except in cases of necessity where a person’s life depends on eating it, such as in the case of starvation where a person fears that he is going to die, and he cannot find any other kind of food, based on the shariah principle: “In cases of necessity, haraam things are permitted.” Qur’an.SurahMa’idah 5:3and Qur’an.Surah An’am 6:119
There is no mention in the shariah (Islamic law) texts of a specific reason for the prohibition on pork, apart from the Ayath in which Allah says (interpretation of the meaning): “for that surely, is impure” Qur’an.Surah An’am 6:145. The word rijs (translated here as ‘impure’) is used to refer to anything that is regarded as abhorrent in Islam and according to the sound human nature (fitrah). 
The pig is one of the filthiest animals on earth. It lives and thrives on muck, faeces and dirt. It is the best scavenger that I know that God has produced. In the villages they don’t have modern toilets and the villagers excrete in the open air. Very often excreta are cleared by pigs.
Some may argue that in advanced countries like Australia, pigs are bred in very clean and hygienic conditions. Even in these hygienic conditions the pigs are kept together in sties. No matter how hard you try to keep them clean they are filthy by nature. They eat and enjoy their own as well as their neighbour’s excreta. 
Among all animal meats pork is the filthiest diet to consume by human beings. Pig is the cradle of harmful germs. Scientific evidences prove that pig meat is least healthy having different harmful agents like Cholesterol and Fatty Acids, Bacteria and Toxins and a number of parasites. The pig meat is high in fat and cholesterol that causes the cardiovascular diseases, obesity, the incidence of large intestine cancer. Bacteria and Toxins associated with pigs spread many diseases like salmonellosis, which leads to the acute gastroenteritis and diarrhea. Many other diseases like, Tuberculosis, Yersiniosis, Listeriosis, Leptospirosis, Brucellosis, Small Pox, Influenza, Anthrax, Balantidial dysentery, Foot rot, Cholera and Erysipeloid are attributed to pork consumption. Parasitic Diseases Ascaris, Ancylostomiasis, Toxoplasmosis, Trichinellosis, Cysticercosis showing signs of mental disorders, pneumonia, bleeding of the lungs (haemoptysis), which may lead to death or madness. The patient may become blind and deaf. Nitrates used in pork and pork products as additives are converted into nitrosamines which cause hepatic cell tumors. Flesh of the pork is hard to digest and may lead to chronic digestive disturbances. Pimples, boils, cysts are common in pork eaters. The pig excretory system secretes 2 percent of its uric acid that is injurious for the human health. Pork consumption seriously affects human health and adversely injurious one’s moral values. A person gets pig like characteristics by eating pork, Indecency, obscenity and vanished honour of women.
Scientific Papers, Animal Science, Series D, vol. LV  
Scientific and medical research has also proven that the pig, among all other animals, is regarded as a carrier of germs that are harmful to the human body. It can cause parasitical diseases, bacterial diseases, viruses and so on.
Pork is regarded as one of the kinds of meat that contain the most cholesterol, an increase of which in the bloodstream leads to an increased likelihood of blocked arteries. The fatty acids in pork are also of an unusual formation, when compared with the fatty acids in other types of food, which makes them more easily absorbed by the body, thus increasing cholesterol levels.
Pork meat and pork fat contribute to the spread of cancers of the colon, rectum, prostate and blood.
Pork meat and pork fat contribute to obesity and related diseases that are difficult to treat.
Eating pork leads to scabies, allergies and stomach ulcers.
Eating pork causes lung infections which result from tapeworms, lungworms and microbial infections of the lungs.
Eating pork that is not thoroughly cooked may also lead to trichinosis (infestation with a hair like nematode worm).  
The "bottom-line" reason for the prohibition of pork consumption is simply that Allah has prohibited it. No specific sanitary or other reason is specified in the Qur’an or Sunnah. We do believe that Allah is al-Hakeem, the Wise, whose orders and prohibitions are not meaningless, but rather contain rationale and wisdom.