infectious diseases
Examples of infectious diseases affecting the skin and eyes
Acne – this term encompasses all follicle-associated lesions, from the isolated pimple to severe widespread acne.
o Comedo: skin swelling over the pore leading out of a hair follicle
o “Whitehead”: a comedo with a closed pore
o “Blackhead”: a comedo with a pore open to the surface of the skin
o Pustule or Papule: a lesion that has erupted on the surface
o Cysts: pustules that come to involve deeper layers of the skin
o Cystic acne: widespread cysts
o Comedo: skin swelling over the pore leading out of a hair follicle
o “Whitehead”: a comedo with a closed pore
o “Blackhead”: a comedo with a pore open to the surface of the skin
o Pustule or Papule: a lesion that has erupted on the surface
o Cysts: pustules that come to involve deeper layers of the skin
o Cystic acne: widespread cysts
Cellulitis – this is a condition caused by a fast-spreading infection in the dermis and in the subcutaneous tissue below. It causes pain, tenderness, swelling, and warmth.
Different Maculopapular Rash Diseases – these include Measles (Rubeoloa), Rubella, Fifth Disease, and Roseola. All of these result in skin rashes, most of which more commonly occur in children.
Conjunctivitis – this is one of the most common eye diseases that occur in humans. It is caused by specific microorganisms that have a predilection for eye tissues, by contaminants that proliferate due to the presence of a contact lens or an eye injury, or by accidental inoculation of the eye by a traumatic event. The best way to prevent this is simply by practicing good hygiene. However, treatments do exist.
River Blindness – this is a chronic helminthic infection, endemic mostly in Latin America, Africa, Asia, and the Midle East. Black flies that carry a filarial helminthic worm often will attack in large numbers and bite up to hundreds a day in the areas common for this infection. The carrier flies are most often found around rural settlements along rivers with overhanging vegetation, hence the disease name.
Examples of infection diseases affecting the Nervous System
Meningitis – this is an inflammation of the meninges. Despite many different microorganisms causing meningitis, the symptoms are all very similar – headache, painful or stiff neck, fever, and usually an increased number of white blood cells in the CSF. There is almost always a treatment or preventative methods, except for in the case of meningitis caused by viruses.
Rabies – this is a slow, progressive zoonotic disease characterized by a fatal encephalitis, escaped only by a handful of people in recent years due to intensive and long-term treatment. There are two forms that ultimately will result to a coma phase that will lead to death due to cardiac or respiratory arrest. The first form is characterized by agitation, disorientation, seizures, and twitching – for all of which the patient is fully aware of. However, the second form is called the “dumb” form, because while the patient is not hyperactive, he/she will be paralyzed, disoriented, and stuporous.
Poliomyelitis – otherwise known commonly as polio, this infection of the spinal cord can cause neuromuscular paralysis. It often affects small children, and in the past was one of the most feared diseases by parents who referred to it as “infantile paralysis.” It wasn’t until the 1950s that a vaccine was created and deemed effective, and even now, WHO (World Health Organization) has been effectively trying to eradicate the polio virus around the world.
Tetanus – commonly known as “lockjaw”, this is a neuromuscular disease that leave the muscles of the body contracting uncontrollably, resulting in spastic paralysis. Death most often occurs due to the eventual paralysis of the respiratory muscles that lead to respiratory arrest. However, this disease has become one of the world’s most preventable diseases due to a very effective vaccine that will usually give protection for about ten years.
Examples of infectious diseases affecting the Cardiovascular and Lymphatic Systems
Plague – deemed the most terrifying of all infectious diseases due to historically deadly pandemics capable of killing millions quickly. Due to the visible darkening of skin, the plague has often been called “black death”, and the last great pandemic occurred in the late 1800s. If left untreated, the result is inevitably death, and even if treated, death rates remain a high 30-50%. The principal agents for transmission are fleas, and while the incidence of disease has been significantly reduced in developed countries, plague still exists (and is even increasing) in large areas of Africa, South America, the Mideast, Asia, and the former Soviet Union. Even in the 1990s, India experienced a large epidemic of plague.
Lyme Disease – although this disease has been found to have been around for centuries, it was not recognized as Lyme disease until the 1970s when an enigmatic cluster of arthritis cases appeared in Old Lyme, Connecticut. It is nonfatal, but it often evolves into a slowly progressive syndrome mimicking neuromuscular and rheumatoid conditions. It is caused by a tick bite, and the lesion that appears characteristically resembles a bull’s eye appearance. Symptoms include fever, headache, stiff neck, and dizziness. If not treated, or even treated too late, it will advance to the second stage which will eventually lead to severe disability as a result of cardiac and neurological symptoms.
Hemorrhagic Fever Diseases – these include Yellow Fever, Dengue Fever, Ebola and Marburg, and Lassa Fever. All of the listed hemorrhagic fevers are caused by viruses in one of the three families: Arenaviridae, Filoviridae, and Flaviviridae.
o Yellow Fever – occurring only in parts of Africa and South America, the patterns of transmission are seen in nature by mosquitoes. This virus will cause capillary fragility and disrupt the blood-clotting system, leading to localized bleeding and shock. The progression of the disease presents a significant mortality rate.
o Dengue Fever – commonly known as the “breakbone fever” due to severe pain in the muscles and joints, this is also carried by mosquitoes. The mild infection is the usual pattern, although a form called dengue hemorrhagic shock syndrome can be lethal. It is endemic to Southeast Asia and India, and several epidemics have occurred in South America and Central America, the Caribbean, and Mexico.
o Ebola and Marburg – while Ebola has received the greatest share of media attention, both disease are similar in nature and transmission, differing from Yellow Fever and Dengue Fever in that the viruses are filoviruses. The diseases are dangerous and appear highly contagious, though the original source and how humans acquire such diseases is still unknown.
o Lassa Fever – in most cases, the infection with this virus is asymptomatic – however, 20% of the cases result in severe hemorrhagic syndrome. This includes chest pain, hemorrhaging, sore throat, back pain, vomiting, diarrhea, and sometimes even encephalitis. Even after recovery, it is common for patients to suffer from deafness. While there is no vaccine, there is a treatment and prevention.
o Yellow Fever – occurring only in parts of Africa and South America, the patterns of transmission are seen in nature by mosquitoes. This virus will cause capillary fragility and disrupt the blood-clotting system, leading to localized bleeding and shock. The progression of the disease presents a significant mortality rate.
o Dengue Fever – commonly known as the “breakbone fever” due to severe pain in the muscles and joints, this is also carried by mosquitoes. The mild infection is the usual pattern, although a form called dengue hemorrhagic shock syndrome can be lethal. It is endemic to Southeast Asia and India, and several epidemics have occurred in South America and Central America, the Caribbean, and Mexico.
o Ebola and Marburg – while Ebola has received the greatest share of media attention, both disease are similar in nature and transmission, differing from Yellow Fever and Dengue Fever in that the viruses are filoviruses. The diseases are dangerous and appear highly contagious, though the original source and how humans acquire such diseases is still unknown.
o Lassa Fever – in most cases, the infection with this virus is asymptomatic – however, 20% of the cases result in severe hemorrhagic syndrome. This includes chest pain, hemorrhaging, sore throat, back pain, vomiting, diarrhea, and sometimes even encephalitis. Even after recovery, it is common for patients to suffer from deafness. While there is no vaccine, there is a treatment and prevention.
Nonhemorrhagic Fever Diseases – these include Brucellosis, Q Fever, Cat-Scratch Disease, and Rocky Mountain Spotted Fever (RMSF). These diseases are characterized by high fever but without the capillary fragility that leads to hemorrhagic symptoms, and all are caused by bacteria.
o Brucellosis – also called Malta fever, undulant fever, and Bang’s disease. It is not designated as being “of highest concern”, and is a common disease of wild herds of bison and elk, and sometimes cattle that share grazing land. While there are several animal vaccines, there is yet to be a vaccine safe or effective enough for humans; however, the infection can be controlled and treated.
o Q Fever – “Q” actually stands for “query”, due to frustration by scientists originally unable to name the source of its cause that was later identified in the mid-1900s. It is acquired largely by environmental contamination and airborne spread as well as infectious materials such as urine, feces and milk. Usually, mild or subclinical cases will resolve spontaneously, although there is treatment for more severe cases.
o Cat-Scratch Disease – the infection is connected with being clawed or bitten by a cat, hence the name. Most infections remain localized and will resolve in a few weeks, although there are effective therapies available and can be prevented easily with a thorough antiseptic cleansing of the cat bite or scratch.
o RMSF – despite being named for the region in which it was first detected, the disease occurs infrequently in the western United States and are more concentrated in the Southeast and eastern seaboard regions. The dog tick appears to be the most responsible for transmission to humans. Symptoms include fever, chills, headache, and muscular pain after 2-4 days, and a spotted rash will also usually occur. If left untreated, the enlarged lesions can merge to become necrotic, predisposing to gangrene of the toes or fingertips. Immediate treatment is required.
o Brucellosis – also called Malta fever, undulant fever, and Bang’s disease. It is not designated as being “of highest concern”, and is a common disease of wild herds of bison and elk, and sometimes cattle that share grazing land. While there are several animal vaccines, there is yet to be a vaccine safe or effective enough for humans; however, the infection can be controlled and treated.
o Q Fever – “Q” actually stands for “query”, due to frustration by scientists originally unable to name the source of its cause that was later identified in the mid-1900s. It is acquired largely by environmental contamination and airborne spread as well as infectious materials such as urine, feces and milk. Usually, mild or subclinical cases will resolve spontaneously, although there is treatment for more severe cases.
o Cat-Scratch Disease – the infection is connected with being clawed or bitten by a cat, hence the name. Most infections remain localized and will resolve in a few weeks, although there are effective therapies available and can be prevented easily with a thorough antiseptic cleansing of the cat bite or scratch.
o RMSF – despite being named for the region in which it was first detected, the disease occurs infrequently in the western United States and are more concentrated in the Southeast and eastern seaboard regions. The dog tick appears to be the most responsible for transmission to humans. Symptoms include fever, chills, headache, and muscular pain after 2-4 days, and a spotted rash will also usually occur. If left untreated, the enlarged lesions can merge to become necrotic, predisposing to gangrene of the toes or fingertips. Immediate treatment is required.
HIV Infection and AIDS – early explanations for this disease centered around the “consequence” of a homosexual lifestyle, as most of the early victims were homosexual males. Given intense research, however, solid and accurate evidence as to the true cause of the disease have helped people to understand that humans originally acquired the disease from eating or skinning chimpanzees. These diseases are easily transmittable through sexual intercourse and transfer of blood or blood products, making the original hypotheses irrelevant, as anyone can acquire the disease no matter their sexual preference. Preventative measures can be taken to decrease the spread, and there are treatments available to prolong life and/or diminish symptoms – however, there is presently still no cure, and the main cause of death for these patients is the characteristic slow destruction of the immune system that will result in a wide variety of infectious and noninfectious conditions.
Examples of infectious diseases affecting the Respiratory System
Rhinitis – more commonly referred to as the “common cold”, occurrences are common in all parts of the world. Symptoms include sneezing, scratchy throat, and runny nose. There is no vaccine for this because a traditional vaccine would need to contain antigens from about 200 viruses for complete protection; also, treatments are symptom-related and usually quite easily remedied.
Influenza – otherwise known as the “flu”, many conditions are erroneously termed “the flu” and it is important to distinguish only diseases caused by influenza are the flu. Symptoms include headache, body aches, fever, chills, dry cough, stuffy nose, sore throat and a general feeling of extreme fatigue. Patients with emphysema or cardiopulmonary disease, along with very young, elderly, or pregnant patients, are more susceptible to serious complications in relation to the flu. Vaccines are available, but they are unique in that the vaccines are only 70-90% effective and are changed slightly every year given that the influenza strains are constantly changing, and a new preventative vaccine is required annually.
Tuberculosis – this disease is an ancient disease, historically referred to as the “Captain of the Men of Death” or the “White Plague,” and even though the risk was significantly reduced in 1943 with the discovery of streptomycin, it has reemerged as a major threat since the 1980s. It is important to note that while humans are easily infected with the bacterium, many may be resistant to the disease with a 5% rate of infected people actually developing a clinical case of TB. While no less dangerous, there are treatments available; however, many patients with TB do not or are unable to comply with the treatments due to poor living conditions. Clinical tuberculosis is divided into primary tuberculosis, secondary tuberculosis, and disseminated tuberculosis (extrapulmonary).
o Primary Tuberculosis – this is the period of hidden infection and it is asymptomatic or accompanied by mild fever. After about 3-4 weeks, the immune system mounts a complex, cell-mediated assault against the bacteria. And although this response further checks spread of infection and helps prevent the disease, it also carries a potential for damage.
o Secondary (Reactivation) Tuberculosis – Despite the usual recovery by patients, live bacteria can remain dormant and become reactivated later, especially with the aid of a weakened immune system. In this type, patients gradually experience more severe and violent symptoms, that is characterized by the gradual wasting of the body, or “consumption”. If left untreated, the disease reaches a 60% mortality rate.
Extrapulmonary Tuberculosis – this is TB infection outside of the lungs and is more common in immunosuppressed patients and young children. Of the organs most commonly involved are the regional lymph nodes, kidneys, long bones, genital tract, brain, and meninges; due to debilitation of the patient and high load of TB bacteria, complications are usually grave.
o Primary Tuberculosis – this is the period of hidden infection and it is asymptomatic or accompanied by mild fever. After about 3-4 weeks, the immune system mounts a complex, cell-mediated assault against the bacteria. And although this response further checks spread of infection and helps prevent the disease, it also carries a potential for damage.
o Secondary (Reactivation) Tuberculosis – Despite the usual recovery by patients, live bacteria can remain dormant and become reactivated later, especially with the aid of a weakened immune system. In this type, patients gradually experience more severe and violent symptoms, that is characterized by the gradual wasting of the body, or “consumption”. If left untreated, the disease reaches a 60% mortality rate.
Extrapulmonary Tuberculosis – this is TB infection outside of the lungs and is more common in immunosuppressed patients and young children. Of the organs most commonly involved are the regional lymph nodes, kidneys, long bones, genital tract, brain, and meninges; due to debilitation of the patient and high load of TB bacteria, complications are usually grave.
Pneumonia – defined as an inflammatory condition of the lung in which fluid fills the alveoli, and due to many types of microorganisms being able to cause this condition, the cases range from mild to severe. Symptoms include runny nose, congestion, headache, often fever, and then the onset of lung symptoms which include chest pain, fever, cough, and discolored sputum production. Preventative measures are usually quite simple, and treatments are available, although for some cases like mycoplasma pneumonia, treatment is not recommended as it is very mild.
Examples of infectious diseases affecting the Gastrointestinal Tract
Diarrhea – there are several types of infectious diseases concerning the GI Tract, but arguably the most important one to look at is diarrhea, which describes frequent loose and watery stools. Diarrhea is very common and usually not serious. Various degrees of diarrhea shall further be discussed:
o Acute Diarrhea – often transmitted by contaminated food by E. coli or Salmonella, it is usually self-limiting, requiring no special treatment.
- Salmonella – most of these strains come from animals and was most commonly associated with poultry. Salmonellosis can be relatively severe (elevated body temperature and septicemia) or mild (vomiting, diarrhea, and mucosal irritation).
- Shigella – Shigella dysenteriae causes the most severe form of dysentery but occurs primarily in the Eastern Hemisphere. Shigellosis symptoms include frequent, water stools, fever, nausea, vomiting, and often intense abdominal pain. If the diarrhea contains blood, it is called dysentery.
- E. Coli O157:H7 (EHEC) – symptoms range from mild gastroenteritis with fever to bloody diarrhea, and about 10% of patients develop hemolytic uremic syndrome (HUS), a sever hemolytic anemia that can cause kidney damage and failure. Also possible are blindness, seizure, an stroke.
o Acute Diarrhea – often transmitted by contaminated food by E. coli or Salmonella, it is usually self-limiting, requiring no special treatment.
- Salmonella – most of these strains come from animals and was most commonly associated with poultry. Salmonellosis can be relatively severe (elevated body temperature and septicemia) or mild (vomiting, diarrhea, and mucosal irritation).
- Shigella – Shigella dysenteriae causes the most severe form of dysentery but occurs primarily in the Eastern Hemisphere. Shigellosis symptoms include frequent, water stools, fever, nausea, vomiting, and often intense abdominal pain. If the diarrhea contains blood, it is called dysentery.
- E. Coli O157:H7 (EHEC) – symptoms range from mild gastroenteritis with fever to bloody diarrhea, and about 10% of patients develop hemolytic uremic syndrome (HUS), a sever hemolytic anemia that can cause kidney damage and failure. Also possible are blindness, seizure, an stroke.
o Acute Diarrhea with Vomiting (Food Poisoning) – food poisoning is suspected when patient has severe nausea, frequent vomiting accompanied by diarrhea, and reports that others who ate the same meal are also suffering the same symptoms. The toxin causing food poising usually comes from Staphylococcus aureus or Bacillus cereus; these toxins can be found in fish, shellfish, or mushrooms. It is important to know the difference between intoxication and infection. Typically, symptoms only last about 24 hours.
- Staphylococcus aureus Exotoxin – associated with eating foods such as custards, sauces, cream pastries, processed meats, chicken salad, or ham that have been contaminated by handling and lack of refrigeration. While not transmissible, a single source can contaminate several people at once. Recovery is very rapid, usually within 24 hours.
- Bacillus cereus Exotoxin – the bacterium is usually found in soil, therefore it is a common resident on vegetables and other products in close contact with soil. It is also linked to fried rice that has been cooked and kept warm for long periods of time. This also has a rapid recovery time.
- Staphylococcus aureus Exotoxin – associated with eating foods such as custards, sauces, cream pastries, processed meats, chicken salad, or ham that have been contaminated by handling and lack of refrigeration. While not transmissible, a single source can contaminate several people at once. Recovery is very rapid, usually within 24 hours.
- Bacillus cereus Exotoxin – the bacterium is usually found in soil, therefore it is a common resident on vegetables and other products in close contact with soil. It is also linked to fried rice that has been cooked and kept warm for long periods of time. This also has a rapid recovery time.
o Chronic Diarrhea – defined as lasting longer than 14 days, the causes for this diarrhea are not completely understood. People suffering from AIDS almost universally suffer from chronic diarrhea, and despite aggressive drug treatment, patients often suffer from this at a high rate.
- Enteroaggregative E. coli (EAEC) – distinguished by its ability to adhere to human cells in aggregates rather than as single cells, though very hard to identify from other E. coli. Its presence appears to stimulate secretion of large amounts of mucus in the gut, and seems to be associated with chronic diarrhea in people who are malnourished.
- Giardia – originally thought to be harmless, it was discovered in the 1950s to be the most common flagellate isolated in clinical specimens concerning diarrhea. While vaccines are readily available to animals, no human vaccine exists; however, there are treatments available.
- Entamoeba – tissue damage by dissolving is the characteristic trait of this, existing in intestinal and extraintestinal forms with the focus on the cecum, appendix, colon, and rectum. There is no vaccine yet, although there are several in development and currently there are effective treatments available. Permanent immunity is unlikely and reinfection can occur.
- Enteroaggregative E. coli (EAEC) – distinguished by its ability to adhere to human cells in aggregates rather than as single cells, though very hard to identify from other E. coli. Its presence appears to stimulate secretion of large amounts of mucus in the gut, and seems to be associated with chronic diarrhea in people who are malnourished.
- Giardia – originally thought to be harmless, it was discovered in the 1950s to be the most common flagellate isolated in clinical specimens concerning diarrhea. While vaccines are readily available to animals, no human vaccine exists; however, there are treatments available.
- Entamoeba – tissue damage by dissolving is the characteristic trait of this, existing in intestinal and extraintestinal forms with the focus on the cecum, appendix, colon, and rectum. There is no vaccine yet, although there are several in development and currently there are effective treatments available. Permanent immunity is unlikely and reinfection can occur.
Helminthic Intestinal Infections – Helminths that parasitize humans range from barely visible roundworms (0.3mm)to huge tapeworms (up to 25m). Although they can cause symptoms that might be mistaken for some of the diseases discussed elsewhere in this chapter, helminthic diseases are usually accompanied by an additional set of symptoms that arise from the host response to helminthes. Most helminthic infections spend part of their lives in the intestinal tract, therefore intestinal distress is the primary symptom. Both tapeworms and roundworms can infect the intestinal tract ins such a way as to cause primary symptoms there.
o Trichuris trichiura – symptoms of infection may include localized hemorrhage of the bowel, caused by worms burrowing and piercing intestinal mucosa.
o Enterobius vermicularis – this pinworm is the most common worm disease of children in temperate zones. Infection is not fatal and most cases are asymptomatic.
o Taenia solium – this tapeworm is transmitted to humans by the consumption of raw or undercooked pork. Other tapeworms of the genus Taenia infect human, including the beef tapeworm Taenia saginata.
o Diphyllobothrium latum – the intermediate host for this tapeworm is fish, and it can be transmitted in raw food such as sushi and sashimi made from salmon.
o Ascaris lumbricoides – an intestinal roundworm that releases eggs in feces, which are then spread to other humans through fecal-oral routes.
o Necator americanus and Ancylostoma duodenale – thse two different nematodes are called by the common name “hookworm.” Hookworm larvae hatch outside the body in soil contaminated with feces and infect by penetrating the skin.
o Strongyloides stercoralis – this nematode infection occurs when soil larvae penetrate the skin, similar to hookworm infestation. The most susceptible are AIDS patients, transplant patients on immunosuppressant drugs, and cancer patients receiving radiation therapy.
o Trichuris trichiura – symptoms of infection may include localized hemorrhage of the bowel, caused by worms burrowing and piercing intestinal mucosa.
o Enterobius vermicularis – this pinworm is the most common worm disease of children in temperate zones. Infection is not fatal and most cases are asymptomatic.
o Taenia solium – this tapeworm is transmitted to humans by the consumption of raw or undercooked pork. Other tapeworms of the genus Taenia infect human, including the beef tapeworm Taenia saginata.
o Diphyllobothrium latum – the intermediate host for this tapeworm is fish, and it can be transmitted in raw food such as sushi and sashimi made from salmon.
o Ascaris lumbricoides – an intestinal roundworm that releases eggs in feces, which are then spread to other humans through fecal-oral routes.
o Necator americanus and Ancylostoma duodenale – thse two different nematodes are called by the common name “hookworm.” Hookworm larvae hatch outside the body in soil contaminated with feces and infect by penetrating the skin.
o Strongyloides stercoralis – this nematode infection occurs when soil larvae penetrate the skin, similar to hookworm infestation. The most susceptible are AIDS patients, transplant patients on immunosuppressant drugs, and cancer patients receiving radiation therapy.
Examples of infectious diseases affecting the Genitourinary System
Urinary Tract Infections (UTIs) – Infection can occur at a number of sites; the bladder (cystitis), the kidneys (pyelonephritis), and the urethra (urethritis). In most cystitis and pyelonephritis cases, the cause is bacteria that are normal biota in the GI tract – most commonly, E. coli, Staphylococcus saprophyticus, and Proteus mirabilis. Community-acquire UTIs are most often transmitted from the GI tract to the urinary system. UTIs are the most common of nosocomial infections. Patients of both sexes who have urinary catheters are susceptible to infections with a variety of microorganisms.
Vaginitis and Vaginoses – Vaginitis is an inflammation of the vagina, most commonly caused by Candida albicans. This is nearly always an opportunistic infection. The bacterium Gardnerella is associated with vaginosis that has a discharge but no inflammation in the agina. Vaginosis could lead to complications such as pelvic inflammatory disease (PID).
Prostatitis – inflammation of the prostate, which can be acute or chronic. Not all cases have been established to have microbial cause, but most have.
Discharge Diseases with Major Manifestation in the GI Tract – Discharge diseases are those in which the infectious agent causes an increase in fluid discharge in the male and female reproductive tracts.
o Gonorrhea – elicits urethritis in males, but many cases are asymptomatic. In females, both the urinary and GI tracts will be infected during sexual intercourse. Major complications occur when the infection reaches uterus and fallopian tubes. One disease resulting from this progression is salpingitis, which can lead to PID.
o Chlamydia – Genital chlamydial infection is the most common reportable infectious disease in the US. In males, the bacterium causes an inflammation of the urethra (NGU). Females hae cervicitis, a discharge, salpingitis, and fregquently PID as a result. Certain strains of chlamydia trachomatis can invade the lymphatic tissues, resulting in another condition called lymphogranuloma venereum.
o Gonorrhea – elicits urethritis in males, but many cases are asymptomatic. In females, both the urinary and GI tracts will be infected during sexual intercourse. Major complications occur when the infection reaches uterus and fallopian tubes. One disease resulting from this progression is salpingitis, which can lead to PID.
o Chlamydia – Genital chlamydial infection is the most common reportable infectious disease in the US. In males, the bacterium causes an inflammation of the urethra (NGU). Females hae cervicitis, a discharge, salpingitis, and fregquently PID as a result. Certain strains of chlamydia trachomatis can invade the lymphatic tissues, resulting in another condition called lymphogranuloma venereum.