Incubation period and Window period in Food-borne diseases and ‘wrong’ biomedical tests.

Getting sick and testing positive to biomedical tests are two related phenomena and are dependent on each other simultaneously in a specified order with one occurring after the other. However, the traditional assertion is that one gets sick, then undergoes a biomedical test and comes off positive at most times and thus sickness comes on before a positive biomedical test and a biomedical test a confirmation of a dis-ease condition. This is not wrong, but not always right at all times.

One only admits to being sick when he/she starts feeling uncomfortable due to several discomforting symptoms accompanying a disease condition, and this is only the period they are pronounced ‘sick’ and a medical attention is thus advised depending on the severity of the condition at hand. Many times the biomedical tests are in correspondence with the individuals or medical professionals' prediction, though sometimes there are deviations as many disease symptoms are very similar, and hence the need for screening and confirmatory test. Anyways, that was such a long story and it’s by the way.

When do we actually get sick?

Headaches, nausea, gastrointestinal tract related issues and a defective energy production conditions are common symptoms of diseases and presents such conditions which makes an individual feel sick, this sets in when the invading pathogen is in its ‘attack’ phase or on the other way round, when the body detects the pathogen via it’s abnormal characteristic or it’s secretions which stimulates the immune system to step into action and make efforts geared towards getting rid of the pathogens. These secreted substances which aids detection of a pathogen are known as chemoattractants.

Chemoattractants in parasitic attacks are foreign particles released by the parasites attacking the body systems, this may include uncommon products of metabolism, eggs or developing larvae of the parasite. In cases of molecular pathogens which are not relatively living particles but mere immunogenes, the body is stimulated to release substances such as platelet activating factors(PAF), histamines, and certain blood clotting factors which stimulates the immune system to act.

Chemoattractants are special substances, via complicated means, they trigger the production of many lytic substances which are part of the immune system. Platelet activating factors triggers the release of platelets, the aggregation of these platelets causes the activation of eosinophils and neutrophils, it is also a potent activator of the complement system.

Eosinophils and neutrophils are powerful lytic cells of the immune system involved in antibody dependent cell mediated Cytotoxicity, while neutrophils are very pronounced in acute inflammation, the eosinophils are the primary arm of the immune system in tackling parasitic attacks. Complements are group of strong lytic proteins produced by the liver hepatocytes in an inactive form known as Zymogens. They are activated by the presence of pathogen associated molecular patterns or damage associated molecular patterns, hence they are only stimulated by immunogenes and damaged cells which are pathogenic, this ensures that no harm is done to normal cells and non-pathogenic body molecules.

How do these make us sick?

Not to complicate things however, the immune actions are complex interactions and are diverse in that many actions are different from the others though they are basically geared towards getting rid of a foreign body. This difference in action gives rise to the different way of tackling pathogens and hence the different symptoms felt due to immune reactions. The action of the immune system is discomforting at most times as it involves a shift in the normal functioning of the body and accompanying homeostatic means centered on restoring the internal conditions to normal.

The presence of microbial agents such as bacteria, viruses, protozoa and fungi, physical agents such as irritants and corrosive chemicals or even a damaged tissue stimulates a non-specific localized immune response which tends to eliminate these infective agents and reconstitute the normal body function, this is known as Inflammation and involves metabolic, cellular and vascular changes in response to the shift in equilibrium which is in congruence with Le Chattelier’s principle. Cellular changes involves the release of cells of immune system which includes neutrophils in acute inflammation and macrophages in chronic inflammation.

Metabolic changes involves a shift in the normal body break down of certain food substances, mainly proteins in response to the infection, this enables the production of guardian proteins such as globulin and albumin which help in the elimination process. Globulins includes immunoglobulins which makes up the antibodies, there’s this an increased globulin production to enable the production of antibodies which serves as receptors, detects the sort and severity of pathogenic attack and relates this to the cells of immune system and to the thymus derived cells (T-cells) which constitutes the cell mediated arm of the immune system and which performs most actions of the immune response and also the discomforts associated with this process. Relation of the details of the pathogens to the cell mediated immune systems is through the binding of the antibodies or complements to certain receptor sites located on these cells, this further differentiates the nature of the disease.

Vascular changes involves the contractions and relaxation of the body vessels in response to the immune reaction, this includes blood vessels and intestinal contractions can also be stimulated by immune responses. These changes accounts for the condition of ‘sickness’, Chemoattractants action induces nausea and it’s subsequent reactions are implicated in many disease condition.

Thus diseases are in a way different from parasitic attacks, while disease involves a deviation from normal body condition due to certain molecules or a shift in the normal composition of the body fluid or an ‘imbalance of the body energy’, parasitic attacks involves something eating you up internally, hence most condition associated with parasitic attacks are due to competition for nutrient and movement of these parasites, a condition known as **larval migrans** this may be cutaneous or visceral but are associated with lesions and prurities. Metabolic products of these parasites are the actual cause of diseases associated with parasitic attacks and not the parasite itself, these metabolic products goes through the same means as the molecular pathogens in causing diseases.

How long does it take to get sick?

Sickness starts off at the time of infection, many sickness and associated symptoms are subclinical such that the effects associated with these infections are not felt by the individual. In some situations, this is because the immune system is strong enough to get rid of the pathogens without causing much noticeable body reactions.

In some unfortunate cases, this is because the antigens causes small doses of infection such that the individual doesn’t feel sick, but actually the body systems are being damaged clandestinely such that the individual only gets sick when very severe damage has already been done to these body systems and organs, these more popular with viral and bacterial attacks and also with opportunistic parasitic attacks where the immune system suppresses these attacks and where the immunogenes avoids causing high titre infections to prevent them from getting noticed by the immune system.

Infection by immunogenes or parasites doesn’t cause diseases immediately, thus most times one doesn’t get sick immediately their body system is invaded by immunogenes. This is due to Incubation periods and Window periods

Incubation period—we’re not ready yet!

Incubation period is the time interval from the actual time of infection to the onset of noticeable symptoms associated with this infection. In oncology, this is also the period from exposure to carcinogens till the period the body develops enough cancerous cells to trigger the body reactions associated with cancer.

Incubation periods can be defined as the time from infection to ‘infectiousness’

Incubation period in parasitic attacks is the time taken for the infecting organism to multiply in number and develop it’s pathogenic features to an extent which would be able to cause reasonable damages to the body.

This comes into play in the case of Food-borne diseases from semi-solid foods and drinks, and the general orientation that the immediate past diet is mostly the cause of the discomfort felt afterwards. Immediate past diets may cause discomfort due to a faulty means of ingestion leading to an impaired intestinal motility and thus the submucosal glands and the intestinal muscles releases secretions and undergoes discomforting contractions respectively which presents as a disease condition.

However this process is physiologic and in no way pathological as it ensures that food particles are conveyed through and to the right parts of the gastrointestinal tract to ensure proper body functioning. Though this process may causes secondary sickness conditions due to allergens which causes hypersensitivity reactions.

However, true Food-borne infections and contraction of parasitic infections would take more time as these infective agents accumulates and multiplies to infective doses which are enough to harm the body, this is however influenced by the dose of the infective agents or number of parasitic larvae in the diet or drink as a higher concentration reduces the incubation period as the infective agents multiples fast and the generation time is reduced in microbial infections.

The route of food ingestion is mainly through the gastrointestinal tract, hence for food related infections, the route of ingestion is the same and plays the same role, however, in case of a different ingestion route, the capacity of the immune system relative to this part of the body plays a huge role in determining the rate of multiplication of the microbes, immunologically privileged sites has little immune system activities going on and thus immunogenes entering through these means would have a reduced incubation period due to an increased host susceptibility and reduced immune response.

The replication ability of the parasite and the invasive ability of the immunogenes and carcinogens is also a huge determinant as the ability to replicate and the speed of replication defers in different microbes and benign tumors are generally less invasive than malignant tumors (this applies in oncology).

Window period and ‘wrong' biomedical tests

The body’s first response to the presence of an immunogen is the production of antibodies in accordance with the clonal selection theory of antibody production, hence antibodies are produced with specificity to the antigen/immunogen which triggered it’s production. Different antigens causes different diseases and this implies that antibodies are specific for this different diseases.

This fact is employed in biomedical diagnostics and most biomedical tests are geared towards detecting these antibodies specific to diseases through professional procedures such as Enzyme Linked Immunosorbent Assay (ELISA) here antigen-antibody reactions are induced in a micro titre well by means of a conjugate which coats the antigens in the micro well and serum which contains antibodies. The micro-titre well is washed after this and a chromogen is poured into the micro-titre well. A change in colour of the chromogen confirms specific immune system reaction for the infection in query.

This is performed for microbial, viral and parasitic infections and have proven functional and relatively cheaper when compared to other diagnostic means such as Polymerase Chain Reaction (PCR), however, something comes into play which have posed a threat to this method of diagnosis— The Window period.

The Window period is the time between the first infection by an immunogen till the time which the body’s immune system produces sufficient antibody to enable the detection of these antibodies during biomedical tests which are dependent on antibody detection. The window period is dependent on the time taken for Seroconversion(time from infection by an antigen till the production of sufficient antibodies) the ability of the immune system to produce antibodies earlier entails a shorter window period and hence detection of the antibodies which makes the tests less tedious.

The window period thus becomes an important factor in biomedical diagnostics as the medical laboratory scientist needs to take this into consideration during diagnosis, even a non-medical professional needs a basic knowledge of the window period as this would enable him/her predict the potentials of an infection after a relatively close exposure to an immunogen.

For a medical laboratory scientist, many technical procedures in disease diagnosis through antibody detection are made more tedious by this concept of window period. Many very correct tests have been pronounced ‘wrong ’ after a re-test is performed some days interval after the first test. When not taken into consideration, the window period leads to the issuance of false negative results as the antibodies have not been sufficiently produced by this time and are undetectable, hence the client is considered negative as regards the infection while he/she is actually infected at this period and have the potential of transmitting the infection.

The window period of different infection differs, the window period for Human Immuno deficiency Virus (HIV) is about three months, hence tests prior to three months from the time of actual infection would produce a false negative results, however, modern diagnostic means have been able to cut down this period to about a month or twelve (12) days depending on the facilities available. The window period of measles infection ranges from 9-12 days while chicken pox virus antibodies are detectable after 9-21 days from actual period of infection.

Hence individuals who have a probability of infections should be tested a period of time which is greater or equal to the window period of the suspected infection or biomedical tests should be performed some intervals which is greater than the window period after the first test to confirm or cancel the possibility of an infection. Individuals who have this knowledge should also be conscious of this time interval and apply for a re-test to ensure freedom from an infection.

References

1.window period~wikipedia

2.incubation period~Wikipedia

3.What is the window period for an HIV test?~i-base

4.Antibody~wikipedia

^{If you write STEM (Science, Technology, Engineering, and Mathematics) related posts, consider joining #steemSTEM on steemit chat or discord here. If you are from Nigeria, you may want to include the #stemng tag in your post. You can visit this blog by @stemng for more details. You can also check this blog post by @steemstem here and this guidelines here for help on how to be a member of @steemstem. Please also check this blog post from @steemstem on proper use of images devoid of copyright issues here.}