This set of diseases are usually caused by insects. We explain what symptoms it causes and what to do if we suffer from it.
This pathology is characterized by symptoms such as fever, abdominal and back pain, cough and reddish skin rashes. The first description of this disease was made in 1498, in the Nasrid kingdom of Granada (Spain), so we know that the causal bacterium has been in close contact with human societies for hundreds of years.
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Due to its relatively high mortality rate and the percentage of the population it affects, knowing the various clinical manifestations of typhus is essential for proper prevention and management. Next, we will tell you in detail everything you need to know about this disease .
Typhus: a disease of bacterial origin
As we have previously anticipated, this pathology responds to a bacterial infection of the Rickettsia genus. We are dealing with multifaceted microorganisms, since they are presented in the form of cocci, bacilli or threads, the latter being the largest (around 10 micrometers).
These bacteria belong to the Gram negative group , and contain both DNA and RNA molecules inside. Phylogenetic analyzes have managed to divide the Rickettsia genus into four well-differentiated groups:
- Group of spotted fevers (R. rickettsii, R. conorii and R. parkeri, among others).
- Typhus group (R. prowazekii and R. typhi).
- Transitional group (R. akari, R. australis and R. felis).
- Ancestral group (R. bellii and R. canadensis).
Due to its clinical and epidemiological importance, we will focus our attention on the species Rickettsia typhi, which is transmitted to humans by the flea species Xenopsylla cheopis, an invertebrate that feeds on the blood of rats. This bacterium is the cause of murine typhus, a pathology that we will see extensively in the following sections.
Figures and affected
In order to understand the severity of the pathology that we show you here, we see it as essential to frame it from a global point of view. The World Health Organization (WHO) and other epidemiological studies show the following data regarding typhus:
- It is estimated that this disease kills one in every 5 million people globally.
- The greatest risk is in poor communities and vulnerable groups, including young children.
- In extensively sampled countries such as Mexico, between 2010 and 2014 more than 300 cases of murine typhus were diagnosed.
- In this same period and country, more than 5,000 cases of epidemic typhus were seen.
- Depending on the clinical variant, typhus can have a mortality rate of 60%.
Although the concept sounds to us like something linked to the 19th century (during Napoleon’s retreat from Moscow in 1812 more soldiers died of typhus than from the war itself), we see with these figures that it is a pathology more than present in today’s society .
As in almost all cases of infectious disease, typhus thrives best in temperate and tropical environments . In addition, various studies have shown that there is a clear correlation between this disease and episodes of natural disasters, such as typhoons or hurricanes, and other socioeconomic factors such as poverty, wars or overcrowding of the population.
Beware of confusion!
It is necessary to emphasize that we are dealing with a pathology caused by bacteria of the Rickettsia genus. It is very common for the general population to confuse typhus with typhoid fever, when they are two totally different diseases.
The second pathology is generated by another bacterium, Salmonella enterica, and this is transmitted through contaminated water and food.
Causes
As we have said before, this disease is spread to people through contact with infected fleas . Contrary to what it may seem, it is not the bite itself that transmits the bacteria in the usual way. In general, the contact between the flea and the human produces an epidermal lesion at the site of the bite, where the flea usually defecates. It is in this scratching of the bite that the person spreads fecal matter through their injury, allowing the bacteria to enter the bloodstream.
It is also necessary to say that these feces can be accidentally inhaled, or inadvertently held on the hands and subsequently rubbed in the eyes. Both routes of transmission are valid, as they allow the bacteria to enter the human body.
It should be noted that the main reservoirs of Rickettsia typhi are the rat species Rattus norvegicus and Rattus rattus, since neither the flea nor the mammal show any symptoms, but both animals remain infective for life. These are not the only known vectors, as typhus can sometimes be contracted from domestic pets such as dogs and cats.
Symptoms
The pathogenesis is very similar in all diseases caused by Rickettsia. These bacteria invade different tissues at the cellular level, but they have a special predilection for the endothelium (tissue that lines the lumen of blood vessels), where they release various cytokines. This produces inflammation in the blood vessels (vasculitis), which leads to characteristic symptoms.
As a response on the part of the human, there is an alteration of capillary permeability (which promotes the outflow of liquid to the tissues) , an alteration of the normal functioning of the organs and coagulation at a local level.
At this point, it is necessary that we correctly distinguish between murine typhus and exanthematous typhus. The first is the one we have been describing up to now, but the exanthematous variant presents certain differences to be pointed out, the main ones being that the causative bacterium in this case is Rickettsia prowazekii and the main vector, the human louse Pediculus humanus corporis. Next, we show you the symptoms of both pathological processes.
1. Murine or endemic typhus
This variant tends to be less intense than its “exanthematous” counterpart , but presents symptoms that are very similar to it. This pathology begins with a prodromal phase (previous malaise) characterized by headaches, asthenia (fatigue) and nausea.
Subsequently, a much more evident clinical picture is manifested, with abdominal and back pain, cough, very high fever (up to 41 degrees), and the appearance of rashes (reddish skin eruptions) that spread to the extremities. In 10% of cases, these skin lesions are accompanied by petechiae, that is, bleeding within the skin.
2. Epidemic or exanthematic typhus
It is interesting to know that, as its name indicates, this variant usually manifests itself in the form of outbreaks or epidemics . It occurs especially in crowded conditions where lice can jump freely between hosts as a result of war, famine or natural disasters.
The probability of complication of murine typhus is 5%, while rash can reach a mortality rate of between 40 and 60% if not treated correctly, which shows that it is a much more serious pathology .
This disease manifests itself with symptoms very similar to the previous one, but new ones appear such as joint pain, low blood pressure and the appearance of lights in the eye focus that can damage the patient’s vision. Common complications are pneumonitis and secondary neurological conditions.
Treatment
Fortunately, typhus is a disease that has a specific treatment with a favorable prognosis . Patients are given tetracycline-type drugs, such as doxycycline, in doses of 100 milligrams every 12 hours for one to two weeks. The administration of chloramphenicol is recommended as a variant in certain cases.
Conclusions
As we have seen, typhus is a disease that has accompanied human beings since ancient times, causing epidemics with thousands of deaths throughout history.
Thanks to the use and standardization of antibiotic drugs, today, diseases like this have drastically reduced their mortality rate. Unfortunately, many low-income and socioeconomically sensitive countries do not have unlimited access to these drugs, leading to preventable deaths.
Bibliographic references
- Garcia-Acosta , J. , & Aguilar-Garcia , CR (2015). Murine or endemic typhus. Internal medicine of Mexico, 31(4).
- García-Acosta, J., Aguilar-García, CR, & Aguilar-Arce, IE (2017). typhus Internal Medicine of Mexico, 33(3), 351-362.
- Nicolás Sánchez, FJ, Ribes Amorós, I., Cervera del Pino, M., Sarrat Nuevo, RM, Bestard Solivellas, J., & Cabau Rubies, J. (2008, January). Cavitated pneumonia due to murine typhus. In Annals of Internal Medicine (Vol. 25, No. 1, pp. 46-47). Arán Editions, SL.
- Murine typhus, CDC. Retrieved July 27 from https://www.cdc.gov/typhus/es/murine/index.html
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.
