DEAR READERS: The deaths of four reindeer from hemorrhagic fever at the Minnesota Zoo last year prompted the zoo to begin running vaccination test trials on susceptible captive species -- some 30 bison, moose and pronghorn antelope -- to protect them against this disease.

As a veterinarian, I applaud this initiative and vigilance. The topic also gave me pause, and prompted the thoughts below.

Hemorrhagic fever is spread by midge flies. The larvae of non-biting midges feed on algae and bacteria, filtering microorganisms out of the water. However, some midges are predators. The larvae of phantom midges live in the open water and prey on water fleas and small larvae. Midge larvae are eaten by fish, dragonfly larvae, water beetles and other predators. Adult midges are eaten by all kinds of things, from spiders to swallows.

Only female midges bite, as they need nutrients from blood in order to produce eggs; those carrying the hemorrhagic fever virus transmit it to livestock and wild animals when they bite and take this blood-meal. In hot climates, midges are known to spread both African horse sickness and bluetongue disease.

Hemorrhagic fever was once prevalent only in the southern states; it was not identified in Minnesota until 2018, on a deer farm. Its northern spread has been attributed to climate change: Wetter and warmer summers provide longer breeding periods for the carrier flies. But I do not believe that climate change alone is responsible. A significant factor is the loss of biodiversity in our urban, suburban and rural environments.

Natural biodiversity helps control pests and pestilence. Specifically, the major predators of midges, such as bats and swallows, have been poisoned in the millions with our insecticides, some of which are now implicated in cancer, Parkinson's and other diseases. Many have also been starved to death by regional insect depopulation efforts, including the use of community sprays and aquatic insecticide pellets to kill mosquito larvae. Orchard and field crop producers of fruits and vegetables, along with state and federal forest departments, often use liberal applications of insecticides to "protect" crops and the timber industry.

We should also add to this list the insecticides that the rains wash off of medicated cattle and other outdoor livestock. These chemicals contaminate the fecal and slaughterhouse waste of pesticide-treated poultry and pigs. The long and short of it is that insecticide chemicals eventually turn up in our drinking water -- and even in the snows on Mount Everest.

Nitrates and phosphates in agrichemical fertilizer, animal manure runoff, and garden and golf course fertilizers, as well as our laundry detergents, all feed toxic algal blooms. These blooms reduce aquatic biodiversity -- plant and animal, vertebrate and invertebrate -- as well as microscopic interdependent life forms.

Our toxic chemicals enter rivers, lakes and oceans, and in freshwater ecosystems, they annihilate virtually all life as they pass up the food chain in increasing accumulation and concentration. Species at the low end of the food chain -- like midge larvae, with few if any aquatic predators that can survive pesticide contamination -- can quickly flourish and develop resistance, as has happened with mosquito larvae. Restoring the health of these natural aquatic ecosystems by phasing out the use of pesticides will go a long way to restoring biodiversity.

Relying only on vaccinations to prevent hemorrhagic fever may protect the livestock industry, as well as the questionable deer farming and hunting industries. But from a One Health perspective, municipal authorities and agricultural and other land-use agencies and regulators need to pay closer attention to disease prevention.

Ecosystems are resilient, and restoration of natural biodiversity mandates reevaluating all pesticide use. This will help control and prevent many diseases and buffer the long-term damage of climate change.

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox’s website at DrFoxOneHealth.com.)

DEAR DR. FOX: I read with interest your article on fish cruelty, and it brought to mind our experiences with fish in the Florida Keys.

When my son was 8 years old, we lived on a canal about 14 miles north of Key West. In our canal lived several schools of fish. One school composed of French grunt, mangrove snapper and several other varieties became very tame, and recognized us. They would jump out of the water and even take food from our hands. My son could lay his hand in the water and one of the fish would lie in it, even when he raised his hand above the water! The fish would lie perfectly still until lowered back into the water.

Wherever we swam in the canal, the school went with us, always surrounding us. Other people would want to feed them or make them do tricks, but the fish did not respond to any of them -- showing us they knew one person from another. I know firsthand that fish have intelligence and feelings, and I hate that others might not have the chance to have the experiences we did.

I have always had a love for animals, birds and insects. When I go into the Everglades, I can get wildlife to come to me -- even insects. Lubber grasshoppers will come when I talk to them, and lizards will also stop and listen. I wish that others would take the time to appreciate the world and its creatures. -- J.W., West Palm Beach, Florida

DEAR J.W.: I know some people will call your communication with other animals delusional, sentimental claptrap, and I pity them -- and anyone else who treats fellow creatures as mere objects. Indeed, when we are quite still around them, most animals will lose their fear, ignore us and get on with their business. They may even show some curiosity and approach us.

To keep animal encounters safe, parents and teachers should provide children with a knowledge of which local species might be dangerous. Make sure they know that many animals have a "flight distance" -- in other words, an invisible circle around them which, if you enter, they will likely flee. Even closer to an animal is the "critical distance," wherein they may attack, or freeze and play dead like an opossum.

How wonderful it can be when wild animals trust us, like the fish with your son! He, no doubt, grew from this communion into a more respectful and compassionate adult than those denied such experiences and parental example. Read on for more thoughts on animals' roles in children's education.

DEAR READERS: Various animal species are still kept in cages and aquariums in schools across the country -- a culturally condoned practice that calls for ethical reexamination. It also raises health concerns, as per the CDC's post entitled "Animals in Schools and Daycares" (visit cdc.gov/healthypets/specific-groups/schools.html).

In a section about preventing the spread of germs in classrooms, the CDC states: "Do not bring reptiles, amphibians, poultry, rodents or ferrets into schools, daycare centers, or other settings with children under 5 years of age."

In 2019, the American Humane Association, the Human-Animal Bond Research Institute and the Pet Care Trust released their "Pets in the Classroom" study. The study's findings suggest that utilization of classroom pets in third and fourth grade U.S. classrooms appears to hold significant benefits for children's social, behavioral and academic development.

I do not doubt these findings, but I do call for alternatives. For humane, ethical and health reasons, no live animals should be kept in classrooms.

Instead, I would love to see every grade-school class given a selection of photos or videos of local animal species, both predators and prey. Students could choose their favorite from each category -- an animal with whom they felt some affinity, awe, affection or wonder. A classroom vote would determine the top choices overall, with these animals becoming the class mascots or icons! Students would then learn all about these animals' behavior, life cycle, ecological importance and conservation status. This would help integrate humane education with ecology and environmental protection.

I also applaud the animal shelters, zoos and wildlife rescue organizations that bring healthy animals to classrooms to tell their stories. It takes some organizational effort, but classroom visits to local wildlife preserves, where children can examine pond and soil life under a microscope, can help them think about and respect other species -- plant, animal and microscopic. Ecology-themed summer camps can do the same.

A new world can open to us when we connect with another species. By "connect," I mean experiencing a spiritual kinship, awe, delight, sympathy or affection -- some special affinity. This is a process all parents should help facilitate as a critical aspect of child development and socialization.

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox’s website at DrFoxOneHealth.com.)

DEAR DR. FOX: I respect your opinions on most all issues, and greatly appreciate your care and concern for animals. Here in south Florida, we have a tremendous problem with Bufo toads, which are highly toxic to dogs, cats and even small children. Many, many dogs are killed by interaction with these creatures. What is your advice on this very serious matter? -- D.W., Jupiter, Florida

DEAR D.W.: I have no quick and simple answers to offer, primarily because most solutions involving poisonous sprays or attractive baits laced with poisons often harm non-target species. Avoidance is the best preventive measure, and we must hope that expanding populations of noxious species will ultimately "crash" due to competition and limitation of natural resources. This could well be the fate of our own noxious species!

Increased rainfall and rising temperatures associated with climate change create ideal conditions for the proliferation of these toxic toads. Cane toads do well in central and south Florida's urban environments, with hundreds of human-made lakes and canals and plenty of bugs year-round. When the rains come, there are even more bugs, and the toads then breed and multiply to cover roads, trails and yards. With no natural predators, they are out-competing indigenous amphibians and small reptiles for food. And like the human-released exotic boas and pythons in the Everglades, in particular, these toads are disrupting the health and biodiversity of ecosystems.

We can blame ourselves, in part, for the proliferation of some species over others by our negative impact on biodiversity and natural habitats, along with our contribution to the climate crisis.

My advice is to prevent companion animals and infants from making contact with these amphibians. This calls for people to be hypervigilant and take every precaution: Never allow unsupervised ventures outdoors, and have yards cleared of dense vegetation that attracts toads. Keep dogs on the leash when out on walks, and keep cats indoors -- or outdoors only in enclosed, toad-proof enclosures or "catios."

D.W. REPLIES: Thanks for the reply, and I respect your opinion very much. However, I have to ask you about solving the problem of getting rid of these invasive creatures, which have no predators. Your reply does not solve the problem. I feel like something has to be done besides avoidance.

Florida Fish and Wildlife says to put Orajel on the toads and put them in your freezer. I think that is ridiculous, and I would appreciate your advice.

During the last year or so, I have had good success in reducing the number of toads in my neighborhood with the use of a pellet gun from very short range. I have since noticed an increased number of tree frogs and other small creatures. My neighbors and myself are still very careful with our dogs, but we have much more peace of mind with fewer Bufo toads.

DEAR D.W.: Catching these toxic cane toads, putting some gel on them and freezing them to death may actually be more humane than hit-or-miss shooting or smashing them to death.

I see no alternative to actual eradication of most invasive and nonindigenous species. This effort would have to employ trained volunteers and animal control and handling experts, depending on the species, by state and federal authorities. This is preferable to relying on local communities and property owners to deal with such matters, which could have negative, unforeseen consequences -- significant animal suffering, accidental human injury, killing of non-target species, etc. In some instances, military sharpshooters are called in, as with the control of feral pigs.

Sometimes making the environment less hospitable, such as removing undergrowth in yards, will reduce toad numbers, just like having secure garbage containers will help reduce raccoon numbers. These methods work community by community without having to apply lethal methods such as poisoned baits and inhumane trapping/relocation.

In other instances, as with coyotes moving to new territories, communities learn to accommodate the animals (as per the protocols of Project Coyote, projectcoyote.org) rather than exterminate. Extermination is not effective in preventing coyote incursion at any rate, and may actually encourage further incursion!

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox’s website at DrFoxOneHealth.com.)