The epidemiology of Treponema pertenue infection is the study of the distribution and determinants of the disease in human populations. According to the search results, some aspects of the epidemiology are:      

• Reservoir: Humans are the only source of Treponema pertenue infection; no known nonhuman reservoirs exist. 
• Transmission: Treponema pertenue infection is transmitted by direct contact with an infected person’s lesion, usually through nonsexual contact such as playing, hugging, or sharing utensils. The disease is most common among children who live in poor and crowded conditions. 
• Distribution: Treponema pertenue infection is endemic in at least 13 tropical countries, mainly Africa, Asia, and Oceania. Almost 85% of infections occurred in Ghana, Papua New Guinea, & the Solomon Islands are the three nations. 
• Incidence and prevalence: Treponema pertenue infection is estimated to be between 46,000 and 500,000 cases yearly.  
• The global prevalence of active infection is estimated to be between 1.5 and 46 million cases. 
• Risk factors: The risk factors for Treponema pertenue infection include poverty, poor hygiene, lack of access to health care, living in rural areas, and having multiple skin lesions. 
• Control and elimination: The control and elimination of Treponema pertenue infection are based on the mass treatment of affected communities with antibiotics such as azithromycin or benzathine penicillin, active surveillance and contact tracing, health education and promotion, and improving sanitation and living conditions. The World Health Organisation (WHO) initiative has started a global campaign to eradicate yaws by 2020. 

Treponema pertenue is a bacterium that causes a chronic and contagious infectious disease called yaws. Yaws primarily affect the skin, bones, and cartilage, causing lesions, deformities, and disabilities if left untreated. Here is the classification and structure of Treponema pertenue: 

Kingdom: Bacteria 

Phylum: Spirochaetes 

Class: Spirochaetes 

Order: Spirochaetales 

Family: Spirochaetaceae 

Genus: Treponema 

Species: Treponema pertenue  

Treponema pertenue’s structure is the bacterium’s physical and molecular organization. According to the search results, the structure of Treponema pertenue is like other treponemes, such as Treponema pallidum, which causes syphilis. Some features of the structure are: 

• Shape: Treponema pertenue is a helically coiled, corkscrew-shaped bacterium. It is 6 to 15 μm long and 0.1 to 0.2 μm wide.   
• Membranes: Treponema pertenue has a double membrane consisting of an outer and inner membrane (also called cytoplasmic membrane). The outer membrane is like that of Gram-negative bacteria. Still, it has a shallow content of surface-exposed proteins, which reduces its antigenicity and makes it harder for antibodies to bind. The inner membrane is like that of other bacteria, and it contains various enzymes and transporters. 
• Flagella: Treponema pertenue has two flagella originating at either end of the organism and pointing inward along its length. The flagella are contained in the periplasmic space between the outer and inner membranes, enabling the bacterium to move with corkscrew motility.   
• Peptidoglycan: Treponema pertenue has a thin layer of peptidoglycan between the outer and inner membranes, which provides structural support and shape to the bacterium. A polymer of sugars & amino acids called peptidoglycan forms a mesh-like network. 
• Protoplasmic cylinder: Treponema pertenue has a protoplasmic cylinder inside the inner membrane, which contains the cytoplasm and the genetic material. The cytoplasm is a material that resembles gel and comprises. 
• various molecules and organelles, such as ribosomes, plasmids, and inclusion bodies. The genetic material consists of a single circular chromosome of DNA that encodes the genes for the bacterium’s functions. 

Antigenic types of Treponema pertenue are the different strains of the bacterium that cause yaws, a skin, bone, and joint illness. From the tropicsAccording to one study, there are at least four antigenic types of T. pertenue based on the reactivity of their surface antigens with monoclonal antibodies.

These antigenic types are like those of Treponema pallidum, the causative agent of syphilis, which suggests a close evolutionary relationship between the two subspecies. However, some antigenic differences between T. pertenue and T. pallidum may explain their distinct clinical manifestations and geographic distribution. 

Different strains of Treponema pertenue have been isolated from humans and animals. Some of the strains that have been sequenced and analyzed are: 

• CDC-2, CDC 2575, Gauthier, Ghana-051, and Samoa D from humans. 
• Fribourg-Blanc and LMNP-1 from baboons. 
• Kampung Dalan K363 and Sei Geringging K403 from Indonesia. 

 Treponema pertenue strains show a great deal of genetic similarity.  However, some genetic differences, such as insertions, deletions, point mutations, and rearrangements, distinguish them. 

The antigens of Treponema pertenue are proteins that can trigger the host’s immune system. Some of the antigens of Treponema pertenue are: 

• Tpp15, Tpp17, and Tpp47, which are also present in TPA. 

• Tpp34, which is unique to TPE. 
• Tpp32, which is like TPA but has a different molecular weight. 

The antigens of Treponema pertenue can cross-react with those of TPA, meaning that they can bind to the same antibodies and cause false-positive results in serological tests for syphilis.  

Therefore, molecular methods such as polymerase chain reaction (PCR) are more reliable for diagnosing Treponema pertenue infection. 

The pathogenesis of Treponema pertenue infection is the process by which the bacterium causes disease in the host. According to the search results, the pathogenesis involves the following steps:   

• Inoculation: Treponema pertenue enters the skin through a minor wound or abrasion, usually because of direct contact with an infected person’s lesion.  
• Multiplication: Treponema pertenue multiplies locally at the site of entry, forming a round, hard swelling of the skin (papilloma) that may break open and form an ulcer.   
• Dissemination: Treponema pertenue spreads through the lymphatic system and blood vessels to other parts of the body, causing secondary lesions on the skin, mucous membranes, bones, and joints.   
• Evasion: Treponema pertenue evades host immune responses by having a low content of surface-exposed proteins on its outer membrane, which reduces its antigenicity and makes it harder for antibodies to bind. It also possesses abundant lipoproteins on its cytoplasmic membrane, which can induce inflammatory processes and cause tissue damage. It also has genetic variability among different strains and antigens, which can confuse the immune system and prevent cross-protection. 
• Persistence: Treponema pertenue can persist in the host for years or decades, causing chronic lesions and complications such as deformity of the bones (especially those of the nose), scarring of large areas of skin due to tissue death, and cardiovascular and neurological problems.   

Host defenses are the mechanisms that the body uses to protect itself from infection. According to the search results, host defenses against Treponema pertenue infection involve cellular and humoral processes. Cellular processes include phagocytosis by macrophages, white blood cells that can engulf and destroy bacteria. Phagocytosis helps to clear treponemes from local sites of infection, such as skin lesions. 

Humoral processes include antibody production by B cells, another type of white blood cell that can identify and attach to specific antigens on the surface of bacteria. Antibodies help to neutralize treponemes and mark them for destruction by other immune cells. However, host defenses are not always effective against Treponema pertenue infection, as the bacterium has evolved strategies to evade immune recognition and response. Some of these strategies are: 

• Having a low content of surface-exposed proteins on the outer membrane reduces antigenicity and makes it harder for antibodies to bind. 
• Possessing abundant lipoproteins on the cytoplasmic membrane can induce inflammatory processes and cause tissue damage. 
• Genetic variability among different strains and antigens can confuse the immune system and prevent cross-protection.   

Treponema pertenue is a bacterium that causes yaws, a tropical skin, bones, and joint infection.   

The clinical manifestations of Treponema infection include: 

• 2 to 5 cm of hard skin swelling in diameter that may break open and form an ulcer. The initial skin lesion typically heals after 3–6 months.  
• Joint and bone pain, fatigue, and new skin lesions that may appear weeks to years after the initial lesion.   
• Thickening and cracking of the skin of the palms of the hands and the soles of the feet. 
• Deformity of the bones (especially those of the nose). 
• Scarring of large areas of skin due to tissue death. 

Treponema infection can also manifest as papules, vesicles, ulcers, and crusting around the external genital organs and, occasionally, the eyes/nose and perineum. 

Treponema pertenue infection can be diagnosed by different methods, depending on the availability of resources and the stage of the disease. Some of the methods are: 

• Clinical examination: The appearance of the skin lesions, such as hard swellings, ulcers, and scars, can suggest Treponema pertenue infection. However, this method is not specific and may be confused with other skin diseases. 
• Dark-field microscopy: A sample of fluid from a lesion can be scraped and examined under a dark-field illumination microscope. This method can reveal the presence of spirochetes, which are spiral-shaped bacteria with corkscrew motility. However, this method requires a fresh sample and a skilled microscopist. 
• Serology: A blood sample can be tested for antibodies against Treponema pertenue using various tests, such as RPR (rapid plasma reagent test), VDRL (venereal disease research laboratory test), TPHA (Treponema pallidum hemagglutination test), or FTA-ABS (fluorescent treponemal antibody absorption test). However, these tests cannot distinguish between previous and current infections or types of treponemal infections, such as syphilis. 
• Polymerase chain reaction (PCR): A sample of fluid or tissue from a lesion can be tested for Treponema pertenue’s DNA using PCR, a technique that amplifies specific segments of DNA. This method is the most accurate and reliable for diagnosing Treponema pertenue infection but requires specialized equipment and trained personnel. 

Treponema pertenue infection can be prevented by various measures, such as: 

• Diagnosing and treating people with the disease and those around them, effectively disrupting the chain of transmission that keeps the bacteria going. 
• Mass treatment of the entire community where the disease is common, using antibiotics such as azithromycin or benzathine penicillin. 
• Improving cleanliness and sanitation, especially washing hands and wounds with soap and water, and avoiding contact with infected lesions. 
• Educating people about the signs and symptoms of the disease and encouraging them to seek medical care if they suspect infection. 
• Monitoring the prevalence and incidence of the disease and reporting any outbreaks to health authorities. 

• Endemic treponemal diseases – PMC (nih.gov) 
• Yaws (who.int)