Reptiles may develop infections from external parasites (mite infestation) and internal bacterial, protozoal or fungal diseases. Open-mouth breathing, pus in the mouth and difficulty eating are common signs of infection.
Metabolic bone disease is a common problem in fast-growing plant-eating reptiles such as lizards and tortoises. It is often caused by poor diet (improper ratio of calcium to phosphorous), lack of UV light and improper husbandry.
Avian paramyxovirus (PPMV) is an RNA virus that causes disease in domestic and feral pigeons. The disease is present in most countries and can spread rapidly. It results in high rates of illness and death in these birds. It can also affect other avian species including poultry. In humans, the infection causes respiratory disease and may result in pneumonia.
PPMV is an enveloped virus with a double-layered lipid membrane and spikes protruding from the inner capsid. The viral genome encodes for a single-stranded RNA molecule that is translated by the host cell’s cellular ribosomes into a protein product. The fusion proteins, F and M, and the attachment protein, H or HN, facilitate viral entry into cells.
Both fusion and attachment proteins contain short cytoplasmic tails that extend from the inner surface of the membrane. These tails are necessary for glycoprotein incorporation into packaged virions and interaction with the matrix protein. The peptide sequences in the tails differ between paramyxovirus members, but they all interact with M through a common domain.
Recent work has suggested that viral fusion and attachment proteins cluster within lipid rafts in the plasma membrane of host cells, which serve as sites for budding virus production. Lipid rafts are enriched in cholesterol and sphingolipids and can form self-assembled domains with a highly ordered structure. This clustering allows specific selection of fusion or attachment proteins to initiate a budding event in the presence of other viral and cellular factors.
Entamoeba histolytica is an anaerobic parasitic amoebozoan, the causative agent of amoebic dysentery and a significant global cause of morbidity and mortality. The disease is endemic in regions with poor sanitation, especially in Asia and Central and South America. The infection can cause amoebic cysts that enter the intestines, where they proliferate and cause diarrhea. In rare complication, the trophozoites breach the intestinal walls and enter the bloodstream, where they can infect parenchymal organs including the liver, heart, lungs, and brain.
Amoebic dysentery is characterized by watery and/or bloody stool, stomach cramping, abdominal pain, and weight loss. A more serious complication is amoebic colitis with bowel perforation and peritonitis.
Invasive amebiasis is exacerbated by immunosuppression, such as from HIV or other infections. Infection begins when humans (the solitary natural host for E. histolytica) ingest the quadrinucleate cysts found in feces and contaminated water. The cysts excyst, releasing trophozoites that invade the colonic mucosa and form distinct flask-shaped ulcers.
Once the trophozoites penetrate the mucosa, they synthesise cystotoxin-like proteins that disrupt cell membranes and destroy cytoplasm. They also secrete cysteine proteases that degrade substrates and the extracellular matrix of the intestinal cells. These proteases also target complement components, resulting in the degradation of tight junction proteins and other host membranes. The trophozoites also engulf apoptotic cells, which contributes to tissue invasion and virulence in vitro.
Pneumonia is an infection that causes the air sacs in one or both lungs to fill with fluid or pus. It’s a serious illness that can be caused by bacteria, viruses or fungi. It can also spread from person to person by breathing in the germs in droplets that come from someone’s sneeze or cough. Infants and people with weak immune systems are at higher risk for pneumonia than others.
Symptoms of pneumonia include fever, cough, shortness of breath, fatigue and a feeling of being sick. People with viral pneumonia often feel milder than those with bacterial pneumonia, but the symptoms usually develop over a period of several days and get worse. They may also have a headache or muscle pain. A complication of pneumonia is bacterial septicemia, in which bacteria from the pneumonia infection enter the bloodstream. This can lead to dangerously low blood pressure and septic shock. Other complications include lung abscesses, a pleural effusion (a buildup of fluid between the lungs), and atelectasis, which is when part or all of the lungs collapse.
Treatment options for pneumonia vary depending on the type of infection, how sick you are and your age. Typically, doctors will give you antibiotics. It’s important to take them as prescribed, even if you start to feel better. If you stop taking them too early, the infection might come back and the germs may become resistant to antibiotics.
Flies lay eggs on living tissue to develop into maggots. These larvae infest the skin and cause myiasis (infection by fly larvae). This is not common in the United States, but it does occur on occasion among people who live in areas with poor hygiene or who travel to those regions. Myiasis can also result from ingestion of maggots that escape from a body cavity and enter the intestines. Infection from these maggots can be fatal.
Symptoms vary depending on the area of the body infested. Those with furuncular myiasis present painful swellings in the genital region or the perineum, while those with craniofacial myiasis are affected by headache and trismus (twitch of the jaw muscles). People infested by the maggots of Cordylobia anthropophaga, another species of human botfly, experience migratory myiasis. In this form, the maggots move through the lower layers of the skin, causing an intensely pruritic erythematous lesion with raised borders. The migratory maggots eventually disappear as they search for a place to molt and die (229).
A 60-year-old male farmer had an ulceration on his leg that was initially smaller but later developed into a larger wound due to the infestation of maggots (figure below). He was treated with oral ivermectin, which is effective against myiasis caused by these dipteran species. Symptoms resolved after treatment.