Repeated infection of cats with Brugia pahangi: parasitological observations.

Cats were repeatedly inoculated with infective larvae of Brugia pahangi. On parasitological grounds they could be divided into 5 groups. Group I--most cats (some 70%) became microfilaraemic (mf+) and retained high levels of microfilariae (mf) in their blood for over 2 years. In some Group I cats mf counts stabilized at high levels whilst in others mf counts continued to increase. Large numbers of fecund adult worms were recovered from their lymphatics. Adult counts were not made on the cats in the current experiments but over 100 adults have been recovered from 'super-susceptible' cats. Large amounts of B. pahangi adult antigen were consistently present in the serum of all Group I cats. About 30% of cats became amicrofilaraemic (mf-). In these cats the peak mf levels were seldom above 10,000 mf/ml. Group II--these cats had less than 10,000 mf/ml and low antigen levels. After more than 1 year of being repeatedly infected B. pahangi adult antigen slowly declined and eventually could no longer be detected in their serum and the number of mf declined very slowly after the fall in antigen levels. This shows that in Group II cats the adult worms die and as the cats are resistant to the development of the continuing weekly inoculation of L3 no new adults can develop. Group III--these cats became mf--during the first year of infection but remained B. pahangi antigen-positive for many weeks after this and, at autopsy, had living adults in their lymphatics.(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating filarial antigen in cats infected with Brugia pahangi is indicative of the presence of adult worms.

Using counterimmunoelectrophoresis with rabbit antisera raised against soluble extracts of adult females of Brugia pahangi parasite antigen was detected in the serum of all cats repeatedly infected with B. pahangi. Antigen was never detected in uninfected cats. The antigen was associated with the presence of adult worms. Antigen was detected consistently in a cat that was amicrofilaraemic but at autopsy harboured only two or three adult worms. Conversely, some cats showed slowly declining numbers of microfilariae and, in these, circulating antigen declined before the number of microfilariae. Eventually no antigen was detectable in circulation whereas microfilariae, although in diminishing numbers, were still present. At autopsy no adult worms were found in these cats. Antigen also appeared in several cats before they became microfilaraemic.

The anthelmintic activity of a novel organic arsenical, R7/45, upon Brugia pahangi in Meriones unguiculatus.

The new organic arsenical R7/45 is a rapidly acting and very potent anthelmintic against adult Brugia pahangi in jirds. Against adult worms implanted into the peritoneal cavity 5 subcutaneous (SC) injections at 2.5 mg/kg of R7/45 killed 100% of adult worms. A single dose SC of 20 mg/kg was 100% effective and 10 mg/kg 76% effective against adult worms. When jirds were autopsied at different times after treatment at 20 mg/kg SC 89% of worms were dead within three days. R7/45 was not active when given by stomach intubation. Pretreatment of jirds with R7/45 had no effect on adult worms subsequently implanted into jirds. R7/45 was highly active against third and fourth stage larvae of B. pahangi in jirds.

Brugia pahangi adults implanted into mice: a possible screen for filaricidal activity.

Brugia pahangi adults grown in the peritoneal cavities of jirds (Meriones unguiculatus) were implanted into the peritoneal cavities of six inbred mouse strains to investigate this system as a screen for detecting filaricidal activity. The mice were given 15 adult B. pahangi and autopsied 35 days later. The recoveries of adult worms were 25%, 35%, 49%, 33%, 26% and 27% of the number implanted respectively for the MF1, TO, NIH, CBA, BALB/c and C3H/HE strains. There was great variation in the number of worms recovered from each strain of mouse. It is concluded that the variation in recoveries was so high that this system is not useful in detecting low level filaricidal activity.

The antifilarial activity of a novel group of organic arsenicals upon Brugia pahangi.

Mel W is a second generation anionic organic arsenical which is filaricidal but has sporadic and unacceptable lethal side effects. Eight new cationic derivatives have now been synthesized in an attempt to avoid the side effects and have been examined for their effects upon adult Brugia pahangi in Meriones unguiculatus. They were all shown to be potent filaricides and the two best compounds, Mel Ga and Mel Cy, were at least 95% effective in killing adult B. pahangi at 5 X 3.13 mg/kg when injected subcutaneously.