Infections and Pathogens Transmitted in Blood | Microbiology

The following points highlight the top three infections occurred due to pathogens transmitted in blood. The three infections are:- 1. Secondary Infection 2. Accidental Infection of Blood Serum Hepatitis and 3. Arthropod Borne Infections.

Infection # 1. Secondary Infection:

Secondary endogenous infection may occur as a result of invasion of blood by pathogenic microor­ganisms after their primary infection through their usual portals of entry. Infections of various parts of the body by microorganisms transmitted through blood from other infected sites, are called as haematogenous infection (e.g. Salmonella typhi) enter pri­marily the body through the consumption of con­taminated water or food and invade secondarily the blood via lymphatic’s and, ultimately, cause the infec­tion in various parts of the body, similarly Tr. pallidum penetrates primarily the body through the mucosa of the genitalia during sexual act and spreads via the blood stream to other parts of the body manifesting the symptoms of secondary syphilis.

Infection # 2. Accidental Infection of Blood Serum Hepatitis:

Hepatitis virus B is present in the blood, saliva, semen, urine of cases and carriers. It is transmitted by accidental or artificial tissue penetration—the splash­ing of blood on the skin, oral mucosa or conjunctiva. Dental operation, vaccine inoculation, tattooing, in­travenous injection of blood, blood products during blood transfusion, shaving may transmit Hepatitis B virus (HBV). As little as 0.0001 ml of the carrier’s blood can transmit the disease. Hepatitis-B virus infection has been reported in nurse, physician, and surgeon by their close contact with the patient.

HBV can be transmitted by the inadequately sterilised syringes and needles used for the labora­tory investigations and blood transfusion. Autoclaving is one of the safest methods of sterilisation, as HBV cannot withstand the autoclave temperature. The transmission of HBV can be avoided by the use of disposable syringes and needles.

Acquired Immunodeficiency Syndrome (AIDS):

A British nurse developed antibodies 45 days after a needle prick while handling AIDS patient. There is clear evidence that the man can infect female sexual partners and there is tentative evidence that the woman can pass the virus to man. The drug- addicts are more likely to catch AIDS, than the sexual partner of an AIDS carrier. Homosexuals, hemophilia and people who inject drugs are at high risk. AIDS virus can be transmitted through the lesions caused by anogenital sex or by hypodermic needle.

Blood Sucking Arthropods (Natural Vectors):

Only female anopheles mosquito can transmit malarial parasites directly into the human blood stream during their blood meal, because of their well- developed strong stout needle proboscis (mouth parts of mosquito).

Infection # 3. Arthropod Borne Infections:

Arthropod (insect with jointed leg) can transmit viral, bacterial, protozoal, helminthic diseases. The dis­eases transmitted by arthropod are called as arthro­pod borne (ARBOR) diseases. Arthropods can act as vectors. The most important classes of the vectors are man biting and animal-biting arthropods.

Based on the mode of the transmission of the disease, arthro­pods may be divided into two groups:

1. Mechanical means:

Those arthropods, which do not bite, are notorious vectors of diseases, as they transmit the diseases mechanically, e.g., house flies walk on feces, boils or sores, soiling their bodies, feet and then they contaminate the eatables. Man ac­quires the infection by consumption of contaminated food.

Many saprophagic (feces-eating) arthropods, flies, ants, cockroaches may ingest intestinal patho­gens while eating infected human faeces. These ar­thropods deposit these pathogens (disease agents) with their faecal droppings on the food or wounds, eyes, lips or skin of human beings. Some insects may also regurgitate (vomit) con­tent of their gut when they bite; subsequently the man gets infected by the pathogens of vomitus.

2. Biological means:

Malarial parasites multiply by sexual reproduction in the gut wall and body of mosquito and, ultimately, transform into sporozoites (infective forms) which accumulate in saliva of mos­quito. Only the sporozoites are infective to man. Simi­larly, biologic means is involved in elephantiasis (filariasis).

Vectors and Diseases Transmitted:

A. Mosquito:

Malaria (Protozoa) Yellow fever (Virus) Dengue (Virus) Encephalitis (Virus) Filariasis (Helminth).

B. Tick:

Rocky Mountain spotted fever (Rickettsia).

C. Flea:

Endemic, typhus (Rickettsia) Bubonic plague (Bacterial).

D. Mite:

Scrub typhus (Rickettsia).

Many arthropod-borne diseases are transmitted to man from animals which are very far away from human dwellings. The diseases transmitted to man from animals are called “Zoonoses”.