GMO Mosquitos Set for Release in California

A previous release of MicroBytes detailed the principles in which several species of mosquitos were genetically modified as a means to control these pests.(1) Another technology by Oxitec prevents Aedes aegypti from reaching adulthood by disrupting the production of essential proteins needed for development.(2) The self-limiting gene passes to offspring, thus reducing wild populations. This article serves to provide additional information as to where and when these mosquitos have been permitted for release.

Aedes aegypti poses a significant threat as they vector diseases including Zika, chikungunya, and dengue fever. There are growing concerns of increased morbidity of these diseases now that this species is established on every continent, excluding Antarctica. The map shown above represents the Centers for Disease Control’s (CDC) best estimate for the potential range of A. aegypti in the United States.(3)

The U.K.-based Oxitec’s technology was approved by the U.S. Environmental Protection Agency (EPA) for deployment in California and Florida. The EPA granted an experimental-use permit for four Californian counties including Fresno, Tulare, Stanislaus, and San Bernardino as well as Monroe County, Florida.(4) A total of 2.4 billion genetically modified mosquitoes are planned for release.(5)

The release of genetically modified A. aegypti will be the Oxitec’s largest release to date. At the time of this report, Oxitec has released more than one billion modified mosquitos globally. This release is scheduled to begin in California this summer. Oxitec’s GMO mosquitos have shown to be more effective than many other control methods. There are high hopes this technology will help mitigate the potential health and environmental impact caused by this invasive pest.

By Trey Jensen

Technical Services Microbiologist

HARDY DIAGNOSTICS

References:

(1)   MicroBYTES, a Microbiology newsletter, Hardy Diagnostics, December 2021.

(2)   Oxitec, How it Works

(3)   Potential Range of Aedes aegypti and Aedes albopictus in the United States, 2017.

(4)   GMO mosquitoes set for release in California to quell disease.

(5)   (4) Why a U.S. Company Plans to Release 2.4 Billion Genetically Modified Mosquitoes

A new use for

an old vaccine

The Bacille Calmette-Guerin (BCG) vaccine was introduced in 1921 as the first vaccination against Mycobacterium tuberculosis (TB). The vaccine was created by attenuating a virulent strain of Mycobacterium bovis via extensive serial passage until safe for intradermal injection. Although it proved to be somewhat effective against TB, the vaccine also demonstrated some remarkable non-specific effects in the vaccinated population.

A 1930’s Swedish study conducted in the TB-burdened province of Norrbotten examined mortalities in BCG-vaccinated and non-vaccinated children from birth up to 12 months. The study showed 22.2% of non-vaccinated children (n=3350) died within 12 months of birth compared to just 6.6% of the BCG-vaccinated population (n=1323). However, the significant correlation between BCG-vaccination and infant mortality rate could not be attributed to protection from TB because TB-related mortalities only accounted for about 2% of deaths. Similar observations have been shown recently in populations including Africa, Bangladesh, and India.(1)

During the initial outbreak of COVID-19, some researchers turned their attention to the potential for inducing non-specific effects against SARS-Cov-2 from BCG booster vaccination. At this time, the Emirates International Hospital offered voluntary booster vaccination of BCG amongst its staff and studied the effects. Of 280 hospital staff examined, 71 opted to get the BCG booster and 209 opted not to. Records show 18 out of 209 of staff persons without a BCG booster tested positive for COVID-19 throughout the study, versus zero positive tests from boosted staff. (2) 

A biological mechanism for BCG-induced non-specific immunity could not be determined from early research, but newer studies provide strong evidence as to what may be happening. A recent hypothesis suggests “heterologous immunity” and “trained immunity” are responsible for BCG’s non-specific effects.

“Heterologous immunity” is the idea that T cells can adapt or cross-react to have effects against unrelated pathogens, and bystander macrophages can be activated after primary infection to heighten immunity against secondary infection. Recent studies indicate that CD8 memory lymphocytes can be activated by cytokines produced during initial stages of secondary infection; completely independent from the presence of the original antigen.(1)

“Trained immunity” refers to the epigenetic changes to innate immune cells induced by exposure to various stimuli, leading to quicker and more robust response from innate immunity cells. This upgraded innate immunity can be demonstrated after exposure to BCG vaccination, certain microorganisms, and other endogenous stimuli.(1)

Not only could the BCG vaccine be used against Covid, but it is currently being used effectively to control bladder cancer as an immune stimulant. (3)

Vaccinations such as BCG that are capable of inducing measurable, non-specific effects against a wide variety of pathogens may play an important role in fighting pandemics such as COVID-19. In the event of another pandemic, deploying an immune-boosting vaccine such as BCG that has already undergone extensive safety testing may be the best strategy at our disposal.

By Manuel Escalera

Performance Studies Technician II

Hardy Diagnostics

References: 1, 2, 3

Worm infested snails pose a threat in Florida

Public health officials have warned about dangerous snails that are carriers of potentially fatal disease.

Eosinophilic meningitis (EM) is a rare disease characterized by meningeal inflammation and eosinophilic pleocytosis in the cerebrospinal fluid. Among the infectious causes of EM is the rare rat lungworm: Angiostrongylus cantonensis. (1) Most documented cases of symptomatic A. cantonesis have occurred in regions of Asia and the Pacific Rim (e.g. Taiwan, Thailand, and the Hawaiian/Pacific Islands). However, widespread geographic dispersal of A. cantonesis is ongoing, facilitated by intercontinental movement of their definitive rodent hosts and the high diversity of potential intermediate hosts. (2)

One of the intermediate hosts is  Lissachatina fulica (the African land snail). This pest has been eradicated in Florida twice – in 1975 and 2021 costing millions of dollars. In 2018, Florida agriculture commissioner described the snails as a “triple threat” because of their potential harm to human health, the environment, and agriculture. (3) In June 2022, the Florida Department of Agriculture and Consumer Services (FDACS) confirmed the reemergence of the giant African land snail, enacted a quarantine, and started treating properties with a metaldehyde based molluscicide (snail bait). Metaldehyde works by disrupting the mucus production, in turn reducing their digestion and mobility making them susceptible to dehydration. (4) In July 2022, the Division of Plant Industry’s Nematology Laboratory confirmed the presence of A. cantonesis in a new population of African land snails in Pasco county, FL.

So, how do humans get infected with A. cantonesis? Most common routes are: ingestion of raw or undercooked snails or slugs; eating raw produce that contains a small infected snail or slug; or possibly slime left by infected snails or slugs. See the life cycle below. Furthermore, there are no readily available blood tests, so the presumptive diagnosis is based on exposure history, clinical signs and symptoms, and laboratory findings of eosinophils in cerebrospinal fluid (CSF). (5)

Finally, to prevent A. cantonesis infection (rat lungworm) one can take the following precautions: avoid eating raw or undercooked shrimp, land crabs, or frogs; inspect and rinse produce in potable water; boil snails, freshwater prawns, crabs and frogs for at least 3-5 minutes; eliminate snails, slugs and rats found near houses and gardens. (6) Even though these types of snails are illegal to distribute, sell and ship across state lines, contact your local state department of agriculture or USDA’s Animal and Plant Health Inspection Service office if spotted. (3) Just remember, if choosing a delicacy such as escargots, when in doubt just say "escar-no."

References: 1, 2, 3, 4, 5, 6

by Francisco Pinon

R&D Microbiologist

Hardy Diagnostics