The American Journal of Tropical Medicine and Hygiene - Volume 12, Issue 5, September 1963

Trophozoites of Entamoeba hartmanni increased significantly in size when they were cultured on an enriched medium. This size increase was not associated with a greater number of binucleate amebae. The greater mean size of E. hartmanni on the enriched medium resulted in a considerable overlap in measurements between culture forms of E. hartmanni and E. histolytica. Since the size increase in E. hartmanni occurred on the first transfer to the enriched medium and continued as long as the amebae were subcultured on it, size is a relatively unstable character in this form and depends to a very great extent upon nutritive conditions. Since E. histolytica and E. hartmanni cannot be separated consistently on the basis of morphological characters or size, it is suggested that a decision on the validity of E. hartmanni as a species distinct from E. histolytica be held in abeyance.

The results of epidemiological, experimental and clinical studies show the existence of two separate forms of cutaneous leishmaniasis caused by two types of Leishmania tropica.

Urban cutaneous leishmaniasis affects humans and dogs, its course is long, and it is avirulent for rodents. Rural cutaneous leishmaniasis is a disease of wild rodents and causes in man sores of rapid onset and short duration.

A newly isolated human strain of Leishmania donovani from Malakal, Sudan, maintained in vivo was used to infect laboratory-reared Phlebotomus papatasi from Cairo and central Sudan. Flies of both strains were successfully infected by feeding through a mouse-skin membrane. Dissections showed nearly 100% infection and a uniformly high intensity of midgut infection (10,000 or more organisms per fly) at days 1 and 2 (the developmental phase), which fell to a lower level (5,000 to 10,000) during days 3 and 4 during division and migration through the gut, followed by rapid loss of leptomonads through the hindgut and diminishing numbers anteriorly on day 5. The numbers decreased to a level of about 100 per fly which was maintained in a decreasing proportion of exposed flies to approximately 20% over the 15-day observation period. Occasional flies showed a cluster of active flagellates at the anterior midgut, even in older infections. The two strains of P. papatasi tested are clearly poor hosts in terms of leptomonad development and survival, and presumably in transmission for the Malakal strain of human L. donovani.

Natural infections were found in 22 (1.88%) of 1,171 wild P. orientalis collected while biting man in a heavily endemic kala azar area of Upper Nile Province in the Sudan, but none of 690 P. papatasi or of local sandflies was infected.

Dissections revealed characteristics of infection in P. orientalis that were quite distinct from those in P. papatasi, with no evidence of a drop in parasite population in older infections, since nearly half the natural infections were at maximum levels in flies captured while taking an additional bloodmeal. Large numbers of both elongate, mature leptomonads and shorter, wider division forms were present. Significantly, there was a preponderance of strong anterior infections, with larger numbers of leptomonads in the cardia than in the stomach in 4 of the 22 flies and a greater concentration of leptomonads in the cardia than in the hindgut in all infected flies, in contrast to some of the laboratory-infected P. papatasi which showed greater concentrations in the hindgut than in the cardia. These observations and related epidemiological investigations clearly suggest that P. orientalis is the vector of human kala azar in this area of the Sudan.

Using lyophilized adult Schistosoma mansoni as emboli, lesions regarded as similar to those of Symmers' fibrosis were produced in the livers of rats. The importance of dead worms in the pathogenesis of hepatic bilharzial fibrosis is emphasized.

Sera taken fortnightly from fourteen patients with eosinophilic lung (tropical eosinophilia) were tested by complement fixation with ethanol extracts of Dirofilaria immitis, Ascaris lumbricoides, Toxocara canis, Gnathostoma procyonis, Fasciola gigantica and Dipylidium caninum. Initially, sera from ten patients had high antibody titers with each of the extracts while antibodies were not detected in sera from the other four; after treatment with diethylcarbamazine the high titers decreased. It is concluded that the reactions obtained with these various extracts do not indicate infection with any particular helminth.

Nearly equal recovery rates of adult worms from Taiwanese monkeys (Macaca cyclopis) infected with Formosan or Japanese strains of Schistosoma japonicum were recorded. Worm recovery rates from the monkeys were low when comparison was made with the highly susceptible laboratory rabbit, signifying only partial susceptibility. Formosan strain granulomas in the liver contained fewer eggs but were considerably more severe and extensive than Japanese strain granulomas. The possibility that the large, atypical granulomas could be reactions to young, degenerating Formosan worms is discussed. An alternative hypothesis to explain the dissimilar reactions, that Formosan strain eggs are stronger tissue irritants than those of the Japanese strain, is proposed.

The Formosan strain of Schistosoma japonicum was passed through the Japanese snail intermediate host (Oncomelania nosophora) for four consecutive generations. Progressively rising rates of snail infection and mortality were recorded. The resultant laboratory strain of Formosan schistosome was used to infect Taiwanese monkeys. Monkeys infected with the natural Formosan strain and natural Japanese strain served as controls. Worm recovery rates were similar in the three groups. Granulomatous responses in the liver produced by the laboratory strain were compared with the large atypical granulomas of the natural Formosan strain and the conventional granulomas of the natural Japanese strain. The new Formosan strain appeared altered toward characteristics possessed by the Japanese strain.

Fifty-five patients with intestinal schistosomiasis were treated with an adult dose of 2 g of sodium antimony dimercapto-succinate (TWSb). Side effects were found to be moderate in severity. At 12 weeks after treatment 15 of 21 African patients and 1 of 16 Europeans were still passing living eggs. The European that was positive at 12 weeks was later negative on repeated followup examinations; thus all Europeans were presumptively cured. The presence of prepatent infections and the occurrence of reinfection were possibly responsible for the high number of apparent failures in the African group.

Aside from considerations of cure-rate, the relative severity of side effects from the drug, its relatively high cost and lack of stability in solution, make it unsuitable for mass treatment under field conditions.

Onchocercal blindness and ocular lesions of onchocerciasis in Liberia are reported for the first time. The order of frequency of onchocercal lesions was as follows: iridocyclitis, complicated cataract, cataract in the young, and secondary glaucoma.

Microfilariae of Onchocerca volvulus were found in the anterior chamber of the eye in 11.8% of 143 subjects with onchocercomata and positive skin biopsies at the outer canthus of the eye. Live microfilariae were recorded within the lens, possibly for the first time.

Onchocercal pannus was infrequent. The absence of trachoma in Liberia is noted.

Punctate keratitis in Liberia is believed to be of viral origin in the majority of cases; however, predilection of the lesions to the limbal area is suggestive of the co-existence of onchocerciasis.

Microfilariae of Onchocerca volvulus are rapidly immobilized when exposed in vitro to cocaine hydrochloride and tetracaine hydrochloride in concentrations normally used for conjunctival anesthesia.

In conjunctival snips the microfilarial count usually rises following instillation of each anesthetic; the rise is marked following cocaine. This indicates that the local anesthetic is selectively absorbed by the tissue and only a small amount comes in contact with the microfilariae. Microfilariae show a positive chemotaxis to concentrations of cocaine that do not impair their motility.

It is shown that local anesthesia with cocaine or tetracaine does not interfere with the diagnostic value of conjunctival biopsies in cases of suspected ocular onchocerciasis, and that instillation with cocaine would seem to offer a better chance of finding microfilariae when their number is small.

An attempt was made to evaluate the bacterial etiology of “summer diarrhea” in infants in Buenos Aires and surrounding areas, from January to March, 1961. Statistical study of 1092 observed cases indicated that the actual percentages (at the 95% reliability level) of enteropathogens in the population with gastrointestinal illness was within the following limits: Salmonella—10.3–14.2%; Shigella—1.4–3.1%; and enteropathogenic Escherichia coli—7.8–11.3%. S. typhimurium and S. newport were the prevalent Salmonella serotypes. Sh. sonnei and Sh. flexneri were the more frequently isolated Shigella serotypes. The majority of enteropathogenic E. coli strains were of the serological types 0111 and 055. In 20 cases two or more enteropathogens were simultaneously isolated.

The nature of the pathogenic flora did not appear to be significantly related to the trophic state. However, Shigella was more frequently found in the more severely dystrophic infants. It was also more frequently found in the severe cases of diarrhea and in the 12–15 month age group.

The existence of Histoplasma capsulatum in Malaya has been established for the first time by its isolation from soil collected in a bat cave.

Two hitherto unknown viruses, for which the names Aura and Una are proposed, have been isolated 14 times from mosquitoes collected in forested areas near Belém, Brazil, during 1959 to 1961. The three strains of Aura were obtained from Culex and Aedes spp., and the 11 strains of Una from Psorophora and Aedes spp. Aura has been shown to be immunologically related to Sindbis and western equine encephalitis viruses and Una to Mayaro and AMM 2021 viruses, all of group A. Three strains of Una virus have also been isolated in Trinidad. A small percentage of sera from residents of the Amazon Valley show HI and neutralizing antibodies against Una. The forest vertebrate hosts of these two viruses are unknown.

When the eighth mouse brain passage of Langat virus was serially propagated in chick embryo tissue cultures, about 70% of the plaquepurified clones prepared from the 12th or 20th passages showed an increased virulence for mice as measured by peripheral infectivity. Such virus clones also caused more severe lesions of the central nervous system in rhesus monkeys inoculated intracerebrally than the virus did before chick embryo tissue culture passage. A serologic comparison of the original Langat virus present in the eighth brain suspension with the viruses present in the 12th or 20th chick embryo tissue cultures, as well as studies of control uninfected tissue culture fluids, showed that the virus present in these chick embryo tissue cultures was Langat virus. Therefore, this increase in virulence was due to Langat virus and not to some latent virus present in the tissue cultures or to a virus picked up by laboratory contamination. When the same original infected mouse brain suspension containing Langat virus was passed in hamster kidney tissue cultures only 3% of the plaque-purified isolates showed an increase in virulence. These results were obtained in a study of 100 plaque-purified isolates grown in chick embryo tissue cultures, 10 isolates being selected from each of 10 tissue culture tubes, and 100 plaque-purified isolates grown in hamster kidney tissue cultures, both types of virus clones being picked in a similar manner.

Further studies on the attenuated TP-21-9 isolate of Langat virus were reported. Of 29 monkeys that were inoculated intracerebrally with high doses of this isolate only one showed evidence of mild lesions in the brain. Histologic examination revealed mild to moderate lesions in the brains of 24 of 28 monkeys inoculated with similar concentrations of the original parent virus.

Spider monkeys inoculated with an attenuated isolate of Langat virus were protected to a great extent when challenged subcutaneously by 6 of 7 remaining members of the Russian spring-summer complex, as evidenced by the suppression of viremia. Although Powassan virus also manifested a lower viremia in monkeys previously inoculated with TP-21-9 virus than in control monkeys, the protection was not as great as that observed against Far Eastern Russian spring-summer encephalitis, louping ill, Omsk hemorrhagic fever, Negishi, or Kyasanur Forest disease viruses. This is in agreement with the observation that Powassan virus is not as closely related serologically to the Russian spring-summer group as other members. However, animals that received a triple vaccination involving the sequential inoculation of three attenuated strains (17D yellow fever, West Nile and Langat viruses) showed excellent protection when challenged by Powassan virus. The attenuated isolate of Langat virus also protected spider monkeys against central nervous system lesions in the brain and spinal cord, caused, under special conditions, by various members of the Russian spring-summer virus complex, and also protected mice against many lethal intraperitoneal doses of all known members of the Russian spring-summer complex. Formalin-inactivated Langat virus vaccine did not protect spider monkeys against challenges by heterologous members of the Russian spring-summer virus complex.

Monkeys immunized orally with the attenuated Langat virus were protected against viremia produced by Kyasanur Forest disease virus.

Spider monkeys inoculated 18 months previously with Langat virus were protected against viremia produced by Far Eastern Russian spring-summer encephalitis virus or Kyasanur Forest disease virus.

The hypothesis that viremia precedes involvement of the central nervous system is discussed.

The present report concerns the susceptibility of three species of insectivorous bats (Tadarida brasiliensis mexicana, Myotis lucifugus lucifugus, Eptesicus fuscus fuscus) to experimental infection with several strains of Japanese B encephalitis (JBE) and St. Louis encephalitis viruses. All three bat species proved to be susceptible to subcutaneous inoculation with one or more virus strains, the intensity of the infection depending on the mouse-passage level and origin of the strain. In general, high mouse-passage strains were less infective for bats than recent isolates. The characteristics of experimental arbovirus infection in bats include a persistent viremia (15–30 days) and viral invasion and multiplication in interscapular brown adipose tissue and, to a lesser degree, in brain and kidney tissue. Intracerebral inoculation of JBE virus produced a more intense and widespread infection in the big brown bat (Eptesicus f. fuscus) than subcutaneous inoculation, yet evidence of viral pathology was not observed in sections of infected brain or brown fat. None of the infected bats showed evidence of disease, indicating that these viruses are capable of replicating in various tissues of the bat without noticeably damaging cells or producing overt signs of encephalitis.

Reasons why bats might be effective reservoirs of arboviruses in various phases of the year-round transmission cycles are discussed and the application of these experimental studies in the planning of field work is indicated.

Adult mice inoculated intracerebrally with a suspension of 17D yellow fever virus were studied by histopathological methods. A myelitis, localized especially in the ventral horns of the lumbar spinal cord, was found. Speculation is made on a possible viral infection through the cerebrospinal fluid, and a similarity with the lesions produced by the poliomyelitis virus in man is pointed out.

The imaginal discs of fourth instar mosquito larvae (Aedes aegypti) and the male and female gonads of diapausing Cynthia pupae were cultivated in vitro. Mosquito larval tissues cultivated in a basic medium, designed for insect tissue culture, yielded a very low percentage of cultures with primary outgrowth. The incorporation into this medium of 10% chick embryo extract increased considerably the number of positive cultures. The incorporation into the medium of extracts from homologous insects had no beneficial effect on growth of tissues from either insect. The cells from the imaginal discs of mosquito larvae supported the proliferation of West Nile virus, whereas the cells from the Cynthia gonads did not.

The capillary tube precipitin test to identify mosquito blood-meals has been modified by use of antisera produced in chickens, and by transporting the frozen abdomens of engorged mosquitoes to the testing laboratory in gelatin capsules. These reagents and techniques increase the rapidity and accuracy of identification of mosquito blood-meals.

Following a bite on the nape of the neck by a female Latrodectus mactans, a 34-year-old Negro developed classic symptoms of acute arachnidism, including diaphoresis, nausea and vomiting, apprehension, and spasm and pain of striated muscles Intravenous injections, 15 minutes apart, each of 10 ml, of 10% calcium gluconate, induced no or only minor improvement. Chlorphenesin carbamate (Maolate®) was administered in doses of two 400-mg tablets about 1 hour after the bite and again 3 hours later. Relief occurred and the patient fell asleep; he had to be awakened for each of two additional doses. It was concluded that the drug deserves further study in arachnidism, to be used as the sole therapeutic agent.

Les Maladies Tropicales dans la Pratique Medicale Courante, by Jean Schneider, Professeur agregé à la Faculté de Médicine de Paris. Preface by G. Lavier. 134 pages, paper back. Masson & Cie. Editors, Libraries de l'Academie de Médicine, 120 Boulevard Saint-Germain, Paris (IV). 1962. 10 NF.

Tables of Representative Values of Foods Commonly Used in Tropical Countries, by B. S. Platt. Privy Council, Medical Research Council Special Report Series No. 302 (Revised edition of Special Report No. 253). 38 pages, paper back. London, Her Majesty's Stationery Office. Agents in America: British Information Services, New York. 1962. $1.40.

Medical Aid to the Developing Countries, Report by a Working Party. Chairman: Sir Arthur Porritt, K.C.M.G., K.C.V.O., C.B.E., President of the Royal College of Surgeons of England. 38 pages, paper back. London, Her Majesty's Stationery Office. Agents in America: British Information Services, New York. 1962. $.40.

This publication, the first of a three volume series on Experimental Chemotherapy, deals mainly with the chemotherapy of protozoan and metazoan infections. Eight of the 22 chapters were written by the editors; the others were prepared by selected biologist collaborators, all with extensive experience in their fields of specialization. The first 4 sections are on general aspects of the subject—history, toxicity, statistical evaluation, and drug resistance. These are followed by chapters on the major parasitic diseases of man and domesticated animals. Included also are sections on anaplasmosis, spirochaetal diseases, and miscellaneous infections. The chapters on specific diseases deal first with the biology of the pathogens and of the infections they produce. Techniques for measuring chemotherapeutic activity in vitro and in vivo are then described. The types of active compounds are reviewed as to structure and efficacy under various test conditions. In many instances, structure-activity relationships, methods of estimation in tissues and body fluids, toxicity data, and mechanism of chemotherapeutic action are reviewed.

As stated in the preface, the authors intended this book to be used by laboratory workers and students, and they have tried, clearly, concisely and in harmonious style, to explain “how” and “why” for most current tests performed in average general hospital laboratories.

The book is attractively printed in offset style, with two columns of text on a page. There are 688 pages of text, 46 pages of index and 333 black and white illustrations, many of which are photographs.

It is customary for reviewers to praise a good book, taking exception, however, to certain errors or omissions, often in their own field of special interest. This gives evidence that the book has been critically read and tends to make for a balanced review. At the risk of appearing undercritical, this reviewer finds this book to be concise, lucid, current, sound, remarkably free from error, and pleasant to read.

This laboratory guide deals with representative parasites, including some of medical importance, selected somewhat on the basis of availability.

Following a short introduction on nomenclature, technical terms and procedures, various groups of parasites are considered in order: Protozoa, Platyhelminthes, Acanthocephala, Nemathelminthes and Arthropoda, divided into orders, families and representative species, illustrated with numerous simple, but excellent, line drawings.

There is a section listing general reference texts and articles, references to articles and monographs on particular parasites and groups, and some leading parasitological journals and abstract publications.

A very useful section on techniques deals with the examination of blood and feces, necropsy of animals, fixation, staining and mounting of ecto- and endo-parasites, and miscellaneous techniques. Most of the techniques described are those in general use but experienced teachers would find it desirable to emend and add to some parts of the section.

In general, the taxonomy and morphology of the representative species selected for study are presented clearly, concisely and accurately, with the frequent use of tables and keys.