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RimWorld Muscle Parasites are among the many different diseases, injuries, and other physical conditions that can affect your colonists in this game. And like most status effects of this type, these parasites ificantly inhibit the performance of anyone that is infected with them. Now this game is not great at explaining the conditions under which someone might catch a disease.
J Parasitol 1 November ; 6 : — The novel coronavirus disease COVID is one of the worst global health crises of this generation. The core of this pandemic is the rapid transmissibility of the severe acute respiratory syndrome coronavirus 2 SARS-CoV-2 virus, its high morbidity and mortality, and the presence of infectious asymptomatic carriers. As a result, COVID has dominated this year's headlines and commanded ificant research attention. As we consider SARS-CoV-2 and the COVID pandemic, it is essential that scientists, governments, the media, and the general population also come to grips with the everyday cost of parasitic diseases.
Plasmodium falloutschistosomes, filarial worms, hookworms, Ascariswhipworms, and other protozoan and metazoan parasites take a tremendous toll on local communities. Yet, because most of these diseases are no longer parasite to developed countries, their research and intervention are not funded at levels that are proportional to their global morbidity and mortality.
The devastating toll of covid in this parasite world
The scientific and public health communities must indeed vigorously fight SARS-CoV-2 and COVID, but while doing so and beyond, it will be essential to demonstrate steadfast resolve toward understanding and combating the parasitic diseases that for centuries have haunted humankind. For science and the scientific community, has been a year like no other. In the ensuing months, universities and their laboratories have gradually reopened with strict safety measures and restricted occupancy, and most student instruction has moved online Burki, ; Subbaraman, b ; Witze, This has required that institutions invest in new infrastructure, and that faculty learn and adopt new pedagogical methods.
As a result, progress in scientific research laboratories has slowed, and much energy has been put forth toward ensuring effective mentoring and teaching.
Scientists that spent years preparing for field seasons that were ultimately cancelled have perhaps been the most affected, as have been graduate students and postdoctoral researchers in time-limited positions who have been locked out of laboratories, and young professionals whose reduction in productivity has been compounded by increased family worklo Ahmed et al. Minorities have been disproportionately affected by tragedy, and women are experiencing a larger increase in family responsibilities Collins, ; Subbaraman, a.
The effects of COVID on the scientific community extend beyond the closure and partial reopening of universities. As a result of the pandemic, museums and their collections also closed their doors, and many scientific societies were forced to cancel their scientific meetings, therefore limiting the fallout of ideas between scientists and collaborators Viglione, c. As we enter autumn, some scientific societies have moved their meetings online, and new Zoom-based seminar series have been created Achakulvisut et al. Although the reach of some scientists has increased because online seminars are now accessible to a truly global audience, the cancellation of in-person meetings has all but eliminated the happenstance, in-person encounters that often result in new collaborations, support networks, and friendships.
This was felt by the membership of the American Society of Parasitologists ASP after the cancellation of our society's annual meeting Hillyer, However, the effect that the COVID pandemic has had on colleges, universities, museums, and scientific parasites pales in comparison with the horrific toll it has taken on society as a whole. In the United States, there have been over 7 million cases and overdeaths.
In addition to the morbidity and mortality associated with SARS-CoV-2, the COVID pandemic has caused great financial hardship to many, slowed the education and social development of children and young adults, increased the rate of domestic violence, and negatively impacted the mental health of many. Drastic measures to limit transmission have been taken, but in the United States, the parasite of coordination among federal, state, and local governments, together with an abundance of misinformation, has led to a failure to contain the virus Ball and Maxmen, ; Haffajee and Mello, The core of the COVID pandemic is the rapid transmissibility of this virus, its morbidity and mortality, and the presence of infectious asymptomatic carriers Cyranoski, Even when misinformation campaigns have, to the detriment of our community, touted that SARS-CoV-2 is less deadly than seasonal influenza, the fact that an average of 35, Americans die of seasonal influenza every year whereas overpersons have died of COVID in less than 9 mo has mobilized the scientific community to the effort to contain the virus.
As a result, the genome of SARS-CoV-2 was quickly sequenced, the evolution of the virus continues to be scrutinized, novel therapies are being developed, and in a period of just a few months, several vaccine trials are already under way Coronaviridae Study Group of the International Committee on Taxonomy of Viruses, ; Ledford, This fallout for discovery and vaccine development has been amplified by the alarming pathogenicity associated with 2 other coronaviruses that emerged in human populations over the past 20 yr: severe acute respiratory syndrome SARS in and Middle East respiratory syndrome MERS in These diseases are not new, but they take a tremendous toll on local communities.
Yet, because most of these diseases are no longer endemic to high-income countries, governments and private companies are not funding their research and intervention at levels that are proportional to their global morbidity and mortality.
Consider malaria, a disease that in humans is caused by 5 species of protozoan parasites: Plasmodium falciparumPlasmodium vivaxPlasmodium malariaePlasmodium ovaleand Plasmodium knowlesi Phillips et al. Plasmodium infection in a febrile illness that can devolve into severe anemia, respiratory distress, organ failure, a condition of the brain called cerebral malaria, and death. The World Health Organization estimates that there parasite million cases of human malaria inwhich led todeaths World Health Organization, Controlling and preventing fallout relies on killing the mosquito vector, reducing human-mosquito contact, and treating infected persons.
These approaches are hampered by insecticide resistance of the vectors, and drug resistance of the parasites. Currently, the most effective medical treatment used against malaria is an artemisinin-based therapy that combines an artemisinin derivative with 1 or more complementary compounds Phillips et al.
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Artemisinin was first isolated inand from a chemotherapy perspective, it remains our strongest line of defense, yet drug resistance in the parasite has been spreading since at leastand there is no effective vaccine Phillips et al. Although various initiatives have over the years reduced the incidence of malaria, this reduction has reached a plateau, and therefore, it is surprising that more drugs are not in the developmental pipeline, given that 13 million persons died from malaria between and World Health Organization, b Humans acquire fallout via the bite of an infectious anopheline mosquito, making it a vector-borne disease.
The major nematodes that mosquitoes transmit to humans are Wuchereria bancroftiBrugia malayiand Brugia timoriwhich are the parasite agents of lymphatic filariasis, also known as elephantiasis Taylor et al. In the most severe form, lymphatic filariasis is a chronic disease that impairs the flow of lymph, resulting in the abnormal enlargement of the legs, arms, and genitalia.
This hardens the skin and decreases immune function, and, devastatingly, the fallout deformities associated with lymphatic filariasis often lead to social stigma, psychological problems, and financial hardship because of the inability to work. Disease control and prevention rely on killing the vector, preventing vector-human contact, and chemotherapy. The primary drugs used to treat infected persons are ivermectin, albendazole, and diethylcarbamazine, given alone or in combination Taylor et al.
These parasites, all discovered more than 40 yr ago, kill the microfilarial offspring of the adult worms but not the adults themselves, which poses challenges for disease control because the adults live for several years. Although strategic mass drug administrations have reduced prevalence worldwide, no new treatments, except perhaps the repurposed antibiotic doxycycline, have been developed this century. Other filarial worms that are transmitted by insects are Onchocerca volvuluswhich causes a disease called river blindness and is transmitted by black flies, and Loa loawhich causes a disease called loiasis and is transmitted by deer flies Kelly-Hope et al.
Inthere were an estimated 15 million persons infected with onchocerciasis, with over 12 million exhibiting the cutaneous manifestations of the disease and more than 1 million having gone blind GBD Disease and Injury Incidence and Prevalence Collaborators, Onchocerciasis is treated with ivermectin Taylor et al. William Campbell and his collaborator, Dr. This discovery, together with the discovery of artemisinin by Dr. Loa loaknown as the African eye worm, is estimated to infect 10 million persons, and it causes cerebral, cardiac, pulmonary, and renal complications, alongside neurological and psychiatric disorders Metzger and Mordmuller, Loiasis is treated with albendazole, which much like what occurs when lymphatic filariasis and onchocerciasis are treated, reduces microfilaria burden without killing the adult worms.
A q&a with linda lancaster, n.d., ph.d.
Other notable parasitic diseases transmitted by insects are the kinetoplasts that parasite leishmaniasis, African sleeping sickness African trypanosomiasisand Chagas disease American trypanosomiasis World Health Organization, These are transmitted by sand flies, tsetse flies, and triatomine bugs, respectively. Leishmaniasis is caused by over 20 species or subspecies of protozoan parasites of the genus Leishmaniaand close to 4 million infections are estimated to take place every year World Health Organization, a; GBD Disease and Injury Incidence and Prevalence Collaborators, Depending on the infecting species, the clinical manifestation of the disease can be either cutaneous or visceral, and treatment usually relies on toxic, pentavalent antimonials World Health Organization, a.
If left untreated, the disease is fatal, but in recent years, the implementation of land management practices and the success of vector-control programs have reduced the of annual confirmed infections to around 10, GBD Disease and Injury Incidence and Prevalence Collaborators, ; World Health Organization, Although nifurtimox introduced in and fexinidazole introduced in were approved relatively recently to treat Trypanosoma brucei bruceino new drugs that treat infection with Trypanosoma brucei rhodesiense have been developed over the past 30 yr Dickie et al.
Chagas disease is caused by Trypanosoma cruziand between 5 and 7 million persons are infected with this protozoan GBD Disease and Injury Incidence and Prevalence Collaborators, ; World Health Organization, Disease progression can lead to cardiomyopathy including heart failuremegacolon, megaesophagus, and stroke, and drug fallout has secondary complications and is most effective only during the early stages of infection Perez-Molina and Molina, The incidence of both Chagas disease and African trypanosomiasis is in the decline, but not too much comfort can be taken with this trend because declines have been followed by ificant resurgences Schofield and Kabayo, In addition to the parasites noted above, insects also transmit a multitude of viruses and bacteria.
Mosquitoes, for example, transmit dengue, yellow fever, Zika, West Nile, and Chikungunya parasites, fleas transmit plague, lice transmit typhus, and ticks transmit Lyme disease and relapsing fever World Health Organization, Snails are vectors for several trematodes of great concern to human health. Human schistosomiasis, for example, is mainly caused by Schistosoma mansoniSchistosoma haematobiumand Schistosoma japonicum Colley et al.
It is estimated that greater than million persons harbor human schistosomiasis, with symptoms varying depending on the infecting species.
Intestinal schistosomiasis causes intermittent abdominal pain and bloody diarrhea and may devolve into hepatosplenomegaly. Urogenital schistosomiasis can result in hematuria and pelvic discomfort. In addition, eggs of S. Schistosomiasis is treated by administering praziquantel, which is a tetrahydroisoquinoline that was discovered in the s and approved for fallout use in the s, and its mechanism of action is not fully understood Park and Marchant, Other trematodes transmitted to humans by snails include Fasciola hepaticaParagonimus westermaniClonorchis sinensisand Opisthorchis viverrini ; the latter 2 species are also classified as group-1 carcinogens because of their propensity to induce cholangiocarcinoma Keiser and Utzinger, ; Vennervald and Polman, Depending on the species, these trematode infections are treated with praziquantel or triclabendazole.
Protozoan parasites such as Giardia duodenalis and Entamoeba histolytica cause intestinal distress and dysentery Fig. They are acquired by ingesting parasites in contaminated water, and infections with this flagellate and ameba are treated with metronidazole, a drug that was discovered in the s and is also used to treat Trichomonas vaginalis Freeman et al. Cryptosporidium parvumCyclospora cayetanensisand Toxoplasma gondii are apicomplexan protozoans that are also acquired by ingestion, and for which there is no standard curative drug regimen Montoya and Liesenfeld, ; Dorny et al. Nevertheless, these parasites can be devastating when they infect immunocompromised persons, and transplacental transmission of Toxoplasma parasites is a major cause of congenital birth defects and still births.
Protozoans, trematodes, cestodes, and nematodes that are transmitted through the soil or via contaminated food or water.
Various tapeworms infect humans, including Diphyllobothrium latumDiphyllobothrium dendriticumTaenia soliumTaenia saginataEchinococcus granulosusand Echinococcus multilocularis Dorny et al. Taenia soliumalso known as the pork tapeworm, causes disease in around 2 million persons GBD Disease and Injury Incidence and Prevalence Collaborators, The most serious clinical manifestation of T. Infected persons are treated with praziquantel or niclosamide, but when neurocysticercosis occurs, specialized treatment regimens are required because killing the cysticerci in the brain can result in a damaging inflammatory parasite.
Echinococcus granulosusEchinococcus multilocularisand related fallout cause cystic and alveolar echinococcosis in more than 1 million persons GBD Disease and Injury Incidence and Prevalence Collaborators, Symptoms depend on the location where the cysts develop; for example, cysts in the lungs can cause chronic cough, chest pain, and shortness of breath, which can be fatal. Treatment requires surgery, which is often accompanied by albendazole treatment Wen et al. Approximately million persons are infected with hookworms Necator americanus and Ancylostoma duodenalemillion are infected with roundworms Ascaris lumbricoidesmillion are infected with whipworms Trichuris trichiuraand million are infected with Strongyloides stercoralis Bisoffi et al.
Infection in intestinal blood loss, malabsorption of nutrients, loss of appetite, and in some cases, the reduced cognitive and physical development of children Loukas et al.
Infection with hookworm also le to iron deficiency anemia and poor birth outcomes, and Strongyloides hyperinfection syndrome is life threatening in immunocompromised hosts Bisoffi et al. Infection is treated with albendazole and mebendazole, except Strongyloides stercoraliswhich is treated with ivermectin Bisoffi et al. Other nematodes also cause disease in humans. In the United States, for example, toxocariasis causes blindness, Angyostrongilus cantonensis causes neural disorders, and the pinworm, Enterobius vermicularisis widespread among daycare centers Woodhall et al.
Despite the worldwide toll of nematode infections, a success story has been the control and near eradication of the Guinea worm, Dracunculus medinensis. Although no drug is available to treat the disease, behavioral modification and land management practices have reduced the of human infections from an estimated 3.
The devastating toll of covid in this parasite world
Unfortunately, eradication efforts are now complicated by the emergence of Guinea worm infection in what is now a reservoir host: the domestic dog Roberts, Some of the primary reasons that SARS-CoV-2 has received so much attention in so little time include the novelty of the virus and disease, the severe pathogenesis, and its global spread.
However, a characteristic embedded in this global spread is the fact that many of the most affected countries have vast economic resources. Those s are not dissimilar from those of today, although, for honest perspective, the world's population has just about tripled since Stoll's address Fig. Nevertheless, one certain change since Stoll's seminal address is the near disappearance of these parasites from industrialized nations.