1. A series of experiments is described in which the transmission of cattle lung-worm infection has been investigated in relation to four different pasture conditions—long grass, short grass produced by gangmowing, grazing by sheep and grazing by resistant cattle.

2. The methods of study of value in this type of field investigation are discussed. It is suggested that the results can be usefully expressed as a series of coefficients which summarize the factors involved in the process of transmission. The methods of calculation of these coefficients are described.

In vector-borne diseases it is generally the vector which determines the success of disease transmission and efforts to limit the incidence of such diseases generally involve control of the vector. The very nature of their feeding habits renders haematophagous arthropods prime candidates for disease transmission and a great deal is now known of the biology of the most important vectors. Nevertheless, there are many areas in which our knowledge is incomplete or about which conflieting views exist.

In a previous paper1 we gave an account of three non-furcocercous cercariae found in Bulinus contortus in the Sudan. During further investigations on the intermediate hosts of Bilharzia, other cercariae have been found in molluscs collected in different districts of the Sudan. As their post-larval development has not been studied, the classification of these cercariae has not been attempted; the procedure of giving them numbers rather than names, indicating specific peculiarities, has been continued.

Through the courtesy of the Editors of Parasitology I have been favoured with an advance proof of the remarks of Dr Woodcock on a former note of mine relating to the procedure of the Recorder of the Protozoa section of the International Catalogue of Scientific Literature and the Zoological Record. In my article I raised three points. (1) In certain cases where the generic names Crithidia and Herpetomonas were placed in inverted commas in the Catalogue, I stated that no direct evidence existed to justify such a procedure. (2) I protested against such meddlesomeness on the part of the Recorder. (3) I stated that the Recorder, who had not worked on the parasites themselves, held, consequently, extreme views. Dr Woodcock's so-called reply has afforded me considerable amusement and it is a matter of surprise to me that he has been so ill-advised as to write such a poor rejoinder—he must know that he has made no answer to my remarks. That the weakness of his position is well known to him is shown by his recourse to the tactics of vituperation and innuendo, where he remarks that my method of criticism is “not straightforward but, on the contrary, distinctly oblique.” Dr Woodcock has no case and so has adopted metaphorically the old, old method of “abusing the plaintiffs attorney,” in the shape of discussing my own papers on parasites not originally under discussion. I am sorry that one who apparently claims to be an authority is reduced to such second-rate methods. While I regret the necessarily severe character of this, my rejoinder, it is impossible to deal otherwise with the numerous side issues raised by Dr Woodcock.

The rocky intertidal zone has a long history of ecological study with barnacles frequently serving as a model system to explore foundational theories. Parasites are often ignored in community ecology studies, and this particularly holds for true for the rocky intertidal zone. We explore the role of the isopod parasite, Hemioniscus balani, on its host, the acorn barnacle, Chthamalus fissus. We use the currencies of biomass and reproduction measured at the individual level, then applied to the population level, to evaluate the importance of this parasite to barnacle populations. We found H. balani can comprise substantial biomass in ‘apparent’ barnacle populations, sometimes even equaling barnacle biomass. Additionally, parasite reproduction sometimes matched barnacle reproduction. Thus, parasites divert substantial energy flow from the barnacle population and to near-shore communities in the form of parasite larvae. Parasites appeared to decrease barnacle reproduction per area. Potentially, this parasite may control barnacle populations, depending on the extent to which heavily infected barnacle populations contribute to barnacle populations at larger scales. These findings regarding the importance of a particular parasite for host population dynamics in this well studied ecosystem call for the integration of disease dynamics into community ecological studies of the rocky intertidal zone.

The new species described here, found in the collections of the Chicago Natural History Museum, was forwarded to me by Harry Hoogstraal, NAMRU-3, Cairo, Egypt, for description. All measurements are given in millimetres.

In the course of recent work on the pathogenicity of Trypanosoma vivax in bovines, cases have occurred at the Veterinary Laboratory, Entebbe, when it has been difficult to diagnose the species of trypanosome occurring in the blood. This difficulty arose because many of the trypanosomes were too small to be typical T. vivax and the possible occurrence of T. uniforme had to be considered, and also because many abnormal degenerate forms appeared at irregular intervals. A more detailed study of the trypanosomes present in the infection was therefore undertaken and, although in many aspects this work is still incomplete, the course of the infection in goats and sheep has been sufficiently interesting to merit this preliminary report.

Amoeba chironomi, nov. sp., is distributed through practically the entire length of the digestive tract of the larva of Chironomus.

The body of A. chironomi varies from 15μ, to 18μ in length and from 10μ. to 12μ in breadth. The single pseudopodium may reach 15μ in length; one pseudopodium only is usually present.

Ectoplasm and endoplasm are well differentiated. A nucleus and a contractile vacuole are present. Food vacuoles are rare. The contractile vacuole resembles an iris diaphragm, consisting of a series of fine, curved, radiating canaliculi, opening into a central space. The excretory products are faintly reddish in colour. The presence of a contractile vacuole is uncommon in parasitic Amoebae.

The nucleus is poor in chromatin. A nucleolus is present.

A. chironomi is highly sensitive to the degree of concentration of the medium in which it lives. Very slight increase in density causes the organism to encyst.

Encystment occurs in the rectum of the host, and the cysts are voided with the faeces. The cysts are from 12μ. to 20μ long and from 9μ broad. The process of encystment is rapid.

The method of cross-infection of the host is probably a “casual” one, viz. by the mouth.

The above-mentioned considerations bearing upon the influence of insect prevalence and the influence of meteorological conditions on the prevalence of trypanosome infections in rats may be summarized as follows:

(1) There are definite seasonal variations in the prevalence of trypanosome infections in M. rattus and in M. decumanus.

(2) No definite correlation is forthcoming between the seasonal prevalence of T. lewisi and the seasonal prevalence of rat fleas. The seasonal prevalence of the transmitting insects is apparently a factor of subsidiary importance in the causation of the trypanosome prevalence.

(3) The evidence adduced above indicates that the dominant factor determining the seasonal prevalence of trypanosome infections is the atmospheric temperature, the optimum temperature approximating to 79° F. It is probable that temperature operates by influencing a developmental cycle of the trypanosomes in the transmitting insects.

(4) It is possible that in addition to temperature the atmospheric humidity may play a part by influencing the direct or mechanical transference of the infection.

The following is a summary of our studies on population of head lice, adults and nits.

1. Out of a total of 8702 adult lice, the male population comprised 2031. The gross infestation rate per head was 129.9 and the maximum number found on a single head was 1434. A disproportion in the distribution of the two sexes was a marked feature.

2. Patients below the age of 11 showed a lower infestation rate than those above this age, and short-haired individuals were more heavily infested than long-haired ones.

3. Frequent combing of the hair and the use of oil did not seem to dislodge the adults or to prevent the females from laying eggs.

4. The maximum larval count on a single head was found to be 4260, the average number of larvae per single head was 418·8, and 9 to 1 was the maximum proportion of larvae to females.

5. The maximum number of nits on a single hair was found to be 17 and 5·06 was calculated as the average number per hair.

6. Treatment with kerosene and pyrethrum killed all the lice and nits, and reinfestation did not occur.

7. The infestation did not spread to healthy patients in the hospital ward; it is thought that the poor migratory habits of lice are responsible for this.

8. From studies on the reinfestation of an individual after treatment it is concluded that head-lice cannot establish themselves on any part of the body except the head, and if their access to the head is prevented, the lice will not survive for more than 24 hr.

An in vitro method for studying radiorespiration has been adapted to single macrofilariae. Using this method viable (but not heat-killed) Dipetalonema viteae and Onchocera gibsoni macrofilariae evolved measurable amounts of 14CO2 from L-[U-14C]glutamine. Nonlinear and less uniform rates of 14CO2 evolution were demonstrated with D-[U-14C]glucose, [1-14C]acetate and [1-14C]octanoate. These findings led us to develop an in vitro screen in which inhibition of 14CO2 evolution from L-[U-14C]glutamine was used as a parameter for gauging macrofilaricidal activity. Using this screen we have examined the activity of 17 ‘so-called’ antifilarial standards and found a greater degree of sensitivity than shown by other biochemical criteria. Other data obtained suggest a role for radiorespirometry in determining the viability of fragments of Onchocerca tissue.

Two new species of coccidia belonging to the genus Wenyonella are diagnosed here by the characters of their oocysts. Wenyonella uelensis and W. parva are geographically related (Uele, Belgian Congo) to the type species, W. africana Hoare (Uganda). By their hosts, two rodents of which one is a terrestrial squirrel, one can relate them to the second species, W. hoarei found in an Indian squirrel by Ray & Das Gupta. W. uelensis is sharply differentiated from the two previously known species, W. africana and W. hoarei, by its oval form, whilst W. parva is noticeably smaller.

We previously reported that blood forms of Trypanosoma cruzi express alpha- and beta-adrenergic receptors and that binding of specific agonists to these receptors modifies the infective capacity of the parasite in vitro. The present study has revealed that the inhibitory effect of the beta-adrenergic agonist L-isoproterenol and the stimulatory effect of the alpha-adrenergic agonist L-phenylephrine are not produced when the parasite is subjected to prolonged exposure to otherwise effective doses of these agonists or when supraoptimal doses of these agonists are used. We refer to these phenomena as ‘desensitization’ because of their analogy with vertebrate cells becoming desensitized by prolonged exposure to, or relatively high concentrations of, adrenergic agonists. At a constant agonist concentration, T. cruzi desensitization was time-dependent and, when the time of parasite treatment with the agonists was not changed, the higher concentrations of the agonist tested were the most effective in producing desensitization. The reduced infectivity resulting from treatment with optimal doses of L-isoproterenol was accompanied by elevated levels of cyclic adenosine mono- phosphate (cAMP) which were not detectable when L-isoproterenol concentrations producing desensitization were used. This finding implicated cAMP as a likely second signal in the inhibitory mechanisms of this agonist. No significant change in cAMP was detectable in parasites treated with L-phenylephrine, leaving open the question about how optimal doses of this alpha-adrenergic agonist enhance T. cruzi infectivity. Parasite responsiveness to alpha- and beta-adrenergic agonists as well as the desensitization effects define a system which regulates infectivity and could be modified at the host tissue level by naturally occurring agonists.

Cochliomyia hominivorax larvae cause myiasis in animals and humans. To register a commercial product to control this dipteran is necessary to experiment on animals. The in vitro test was standardized to evaluate the larvicidal efficacy of commercial topical products. Five formulations were analysed in vitro and in vivo. For the in vitro test, a colony was formed and three replicates (n = 200) of each larval stage (L1, L2 and L3) were treated. The viability of the larvae was evaluated after 5 and 30 min, and at 1, 2, 6, 12, 24, 48, 60 and 72 h post-treatment (HPT). For the in vivo test, 30 bovines divided into six groups were castrated to achieve natural infestation with C. hominivorax. Animals in the treated groups received the product. Myiasis and efficacy were evaluated 12, 24, 36, 48, 60 and 72 HPT. Four formulations tested in the in vitro test achieved 100% efficacy at 24 HPT. In the in vivo experiment only one achieved 100% efficacy at 24 HPT. However, all products achieved the maximum efficacy by the end of study. The in vitro test developed here could be adopted to evaluate the efficacy of topical products for the control of C. hominivorax larvae.

Toxoplasma gondii is an apicomplexan intracellular protozoan parasite responsible for toxoplasmosis, a disease with considerable medical and economic impact worldwide. Toxoplasma gondii cells never lose the nuclear envelope and their chromosomes do not condense. Here, we tested the murine monoclonal antibody PL2-6, which labels epichromatin (a conformational chromatin epitope based on histones H2A and H2B complexed with DNA), in T. gondii cultured in human fibroblasts. This epitope is present at the exterior chromatin surface of interphase nuclei and on the periphery of mitotic chromosomes in higher eukaryotes. PL2-6 reacted with T. gondii H2A and H2B histones in Western blot (WB) assays. In addition, the antibody reacted with the nuclear fraction of tachyzoites, as a single band coincident with H2B histone. In the T. gondii tachyzoite stage, PL2-6 also had peripheral nuclear localization, as observed by epifluorescence/confocal microscopy and immunoelectron microscopy. Confocal analysis showed that epichromatin is slightly polarized to one face of the parasite exterior chromatin surface. In replicating tachyzoites, PL2-6 also labels the exterior chromatin surface, covering the face of both segregating nuclei, facing the plasma membrane of the mother cell. The possible role of epichromatin in T. gondii is discussed.

In November 1912, through the courtesy of Mr S. W. J. Scholefield, Prof. Nuttall received fourteen living nymphs of Argas brumpti from Kitui, British East Africa. As only the adults and later stage nymphs of this species are known, an attempt was made to raise the species in the laboratory.

The examination of a vast number of ticks, collected in late years from various hosts in many parts of the world, has resulted in the addition of several new species to the genus Haemaphysalis. Though only 13 of the species admitted by Neumann in his “Révision” (Pt. II, 1897) still stand, the number of recognised good species now reaches 43.

In May 1912 when on the way with our Floating Laboratory to Rejaf, en route for the sleeping sickness district in what was formerly the Lado Enclave (now part of Mongalla Province), the late Colonel Mathias shot, near Renkwood station on the White Nile, two specimens of the Senegal or red-fronted gazelle—Gazella rufifrons. I found one of these animals, a female in good condition, heavily infected with sarcosporidiosis, the diaphragm, the intercosted muscles and those of the thigh being specially affected, though the striped muscle fibre everywhere contained cysts in varying numbers. In the light of the observations made by Probst and Francis (1910) the blood was carefully examined but no sarcosporidial spores were found in it nor were any blood parasites present.