PREPATOGENIC PERIOD OF THE DISEASE: NATURAL HISTORY, EXAMPLE - MEDICINE - 2025

The prepatogenic period is the initial period or stage of the natural history of a disease in humans. At this stage there are no clinical manifestations of the disease or cellular, tissue or organic changes.

This period refers to all factors related to the causative agent and the environment or the host itself that predispose or favor the latter entering the natural course of a disease. In other words, during this stage, the causative agent has not come into contact with the host, but the factors that favor that contact are present in the environment.

Photograph of a sick woman (Image by Mojca JJ at www.pixabay.com)

The knowledge of all the factors related to this initial prepatogenic stage of a disease allows to apply effective preventive measures and combat, as far as possible, the risk factors of the host. The main agents.

Main agents of the prepatogenic period

During the prepatogenic period of the disease, the following protagonists should be noted:

- A host is any living organism capable of harboring the causal agent of a disease.

- Causal agent is any living organism or substance whose presence in the host is the cause of a disease.

- Environment is the set of external conditions that affect the life and development of an individual and that are related to the host's disease.

Natural history of a disease

The natural history of a disease refers to the natural course, without external intervention, of a pathological process from the moment in which the factors of the host, the causative agent and the environment come together to get in contact with the host. So until the natural outcome of the disease, which can end with death, chronicity or cure.

In the natural history of any disease, some periods can be verified, two of which can be distinguished: the prepatogenic or susceptibility period and the postpathogenic period. In turn, the latter can be subdivided into a subclinical stage and a clinical stage.

In the subclinical stage, for communicable infectious diseases, we speak of the incubation period, which is the period in which the infectious agent invades the host, reproduces and / or begins to produce toxins. In slowly progressive degenerative diseases, this period is called the latency period.

In the subclinical stage, the causative agent has contacted the host, but there are still no clinical manifestations of the disease. This stage can last hours or days if it is an incubation period, or months and even years in the case of a latency period.

Then the clinical stage appears, which can be divided into three periods: prodromal, clinical, and resolution.

The first refers to the appearance of the first signs and symptoms of the disease. In the clinical period, the specific signs and symptoms appear that allow making the diagnosis and applying the treatment. In the resolution stage, healing may occur, a chronic state, or the death of the host.

Example

Next, use will be made of an example of a pathological condition, specifically lead poisoning, which will make it possible to explain in a "graphic" way the stages of the natural history of a disease, especially the prepatogenic stage.

The case

In the late 1940s, the United States replaced lead with titanium for interior paints because lead was believed to be toxic to children. However, lead-based paints were used between the 1940s and 1960s to paint the interior of houses.

This was because it was not possible to prevent the use of lead-based exterior paints to paint the interior of houses, nor to prevent the use of dilapidated houses built and painted before the prohibition date.

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In old and dilapidated houses and apartments in poor urban areas or in rural areas, the paint that peels off the walls can be ingested by young children, especially if the child suffers from the so-called “pica”.

The “pica” is classified for children older than 24 months as an eating disorder in which the young person suffers from an irresistible compulsion or desire to lick or consume inedible substances.

The substances they most frequently consume or lick are chalk, dirt, ice, plaster, paint chips, baking soda, glue, starch, cigarette ash, mold, paper, or anything else of no nutritional value and potentially toxic.

The presence of lead paint, and especially of paint in poor condition that comes off easily from the walls, and the presence of a child with an itch living in that environment, makes the conditions of the host, the causal agent and the environment concur for contamination to occur.

Under these conditions, the host with the pica, the environment that has bad paint and the causative agent (lead) are found together and this concurrence of factors forms the prepatogenic or susceptibility stage for lead poisoning.

"Peeling" paint from a wall (Image by ShonEjai at www.pixabay.com)

Evolution of the disease

When the child ingests lead paint, he does not initially present symptoms, he is in the subclinical or asymptomatic stage. But as the child continues to consume lead, it accumulates in their tissues.

Finally, symptoms appear and the child enters the clinical stage of the natural history of the disease. Those symptoms are loss of appetite, vomiting, irritability, incoordination, and abdominal pain.

Later, there may be signs of lead encephalopathy with cerebral edema and seizures, which can lead to the death of the child if not treated in time.

Treatment

Given the clinical signs and symptoms, the diagnosis can be made and treatment with chelating agents is prescribed. If treatment is instituted on time and lead is removed from the environment or the child is separated from the high-risk environment, permanent damage can be reduced.

If the treatment is delayed, the disease can evolve into a chronic situation in which permanent residual damage occurs, such as delayed intellectual development and learning problems, among others. That is, the disability stage is passed. If, in addition, lead consumption continues, the child dies.

In this case, primary prevention would theoretically consist of treating and eliminating the pica and eliminating lead from the environment where the child lives, before contamination occurs.

References

1. de Arruda, GO, da Silva Barreto, M., & Marcon, SS (2015). Perception of adult men on their preventive practices and health support networks. Revista da Rede de Enfermagem do Nordeste, 16 (3).
2. Hutchinson, GB (1960). Evaluation of preventive services. Journal of Chronic Diseases, 11 (5), 497-508.
3. John, ML (2001). A dictionary of epidemiology. Oxford University Press.
4. Mausner, JS, & Bahn, AK (1974). Epidemiology. An introductory text.
5. Sackett, DL, Haynes, RB, Tugwell, P., & Guyatt, GH (1985). Clinical epidemiology: a basic science for clinical medicine (pp. 59-138). Boston: Little, Brown.
6. Sackett, DL, Haynes, RB, Tugwell, P., & Guyatt, GH (1985). Clinical epidemiology: a basic science for clinical medicine (pp. 59-138). Boston: Little, Brown.